Linear Integrated Ciruits - 2 Marks Question Bank - Iv Sem Ece f3n
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Linear Integrated Circuits
LINEAR INTEGRATED CIRCUITS
VVCET – Dept. of ECE
Linear Integrated Circuits
080290022 - LINEAR INTEGRATED CIRCUITS AIM: To teach the basic concepts in the design of electronic circuits using linear integrated circuits and their applications in the processing of analog signals. OBJECTIVES • To introduce the basic building blocks of linear integrated circuits. • To teach the linear and non-linear applications of operational amplifiers. • To introduce the theory and applications of analog multipliers and PLL. • To teach the theory of ADC and DAC • To introduce the concepts of waveform generation and introduce some special function ICs. UNIT - I IC FABRICATION AND CIRCUIT CONFIGURATION FOR LINEAR ICS Advantages of Ics over discrete components – Manufacturing process of monolithic Ics – Construction of monolithic bipolar transistor – Monolithic diodes – Integrated Resistors – Monolithic Capacitors – Inductors. Current mirror and current sources, Current sources as active loads, Voltage sources, Voltage References, BJT Differential amplifier with active loads, General operational amplifier stages -and internal circuit diagrams of IC 741, DC and AC performance characteristics, slew rate, Open and closed loop configurations. UNIT - II APPLICATIONS OF OPERATIONAL AMPLIFIERS Sign Changer, Scale Changer, Phase Shift Circuits, Voltage Follower, V-to-I and I-to-V converters, adder, subtractor, Instrumentation amplifier, Integrator, Differentiator, Logarithmic amplifier, Antilogarithmic amplifier, Comparators, Schmitt trigger, Precision rectifier, peak detector, clipper and clamper, Low-, high- and band- Butterworth filters. UNIT - III ANALOG MULTIPLIER AND PLL Analog Multiplier using Emitter Coupled Transistor Pair - Gilbert Multiplier cell – Variable transconductance technique, analog multiplier ICs and their applications, Operation of the basic PLL, Closed loop analysis, Voltage controlled oscillator, Monolithic PLL IC 565, application of PLL for AM detection, FM detection, FSK modulation and demodulation and Frequency synthesizing. UNIT - IV ANALOG TO DIGITAL AND DIGITAL TO ANALOG CONVERTERS Analog and Digital Data Conversions, D/A converter – specifications - weighted resistor type, R2R Ladder type, Voltage Mode and Current-Mode R-2R Ladder types - switches for D/A converters, high speed sample-and-hold circuits, A/D Converters – specifications - Flash type Successive Approximation type - Single Slope type – Dual Slope type - A/D Converter using Voltage-to-Time Conversion - Over-sampling A/D Converters. UNIT - V WAVEFORM GENERATORS AND SPECIAL FUNCTION ICs Sine-wave generators, Multivibrators and Triangular wave generator, Saw-tooth wave generator, ICL8038 function generator, Timer IC 555, IC Voltage regulators – Three terminal fixed and adjustable voltage regulators - IC 723 general purpose regulator – Monolithic switching regulator, Switched capacitor filter IC MF10, Frequency to Voltage and Voltage to Frequency converters, Audio Power amplifier, Video Amplifier, Isolation Amplifier, Opto-couplers and fibre optic IC. TEXT BOOKS: 1. Sergio Franco, Design with operational amplifiers and anategrated circuits, 3rd Edition, Tata McGraw-Hill, 2007. 2. D.Roy Choudhry, Shail Jain, Linear Integrated Circuits, New Age International Pvt. Ltd., 2000. REFERENCES: 1. B.S.Sonde, System design using Integrated Circuits , New Age Pub, 2nd Edition, 2001 2. Gray and Meyer, Analysis and Design of Anategrated Circuits, Wiley International, 2005. 3. Ramakant A.Gayakwad, OP-AMP and Linear ICs, Prentice Hall / Pearson Education, 4th Edition, 2001. 4. J.Michael Jacob, Applications and Design with Anategrated Circuits, Prentice Hall of India, 1996. 5. William D.Stanley, Operational Amplifiers with Linear Integrated Circuits, Pearson Education, 2004. 6. K Lal Kishore, Operational Amplifier and Linear Integrated Circuits, Pearson Education, 2006. 7. S.Salivahanan & V.S. Kanchana Bhaskaran, Linear Integrated Circuits, TMH, 2008.
VVCET – Dept. of ECE
Linear Integrated Circuits
UNIT-I CIRCUIT CONFIGURATION FOR LINEAR ICs 1. Define an Integrated circuit. An integrated circuit(IC) is a miniature, low cost electronic circuit consisting of active and ive components fabricated together on a single crystal of silicon. The active components are transistors and diodes and ive components are resistors and capacitors. 2. Mention the advantages of integrated circuits. • Miniaturisation and hence increased equipment density. • Cost reduction due to batch processing. • Increased system reliability due to the elimination of soldered ts. • Improved functional performance doe to Matched devices. • Increased operating speeds. • Reduction in power consumption. 3. Write down the various processes used to fabricate IC’s using silicon planar technology. • Silicon wafer preparation. • Epitaxial growth • Oxidation. • Photolithography. • Diffusion. • Ion implantation. • Isolation. • Metallisation. • Assembly processing and packaging. 4. List out the steps used in the preparation of Si – wafers. • Crystal growth &doping • Ingot trimming & grinding • Ingot slicing • Wafer policing & etching • Wafer cleaning 5. What is the purpose of oxidation? • SiO2 is an extremely hard protective coating and is unaffected by almost all reagents. • By selective etching of SiO2, diffusion of impurities through carefully defined windows can be accomplished to fabricate various components. 6. What are the two important properties of SiO2? • SiO2 is an extremely hard protective coatng & is unaffected by almost all reagents except by hydrochloric acid. Thus it stands against any contamination. • By selective etching of SiO2 , diffusion of impurities through carefully defined windows in the SiO2 can be accomplished to fabricate various components. 7. Why aluminium is preferred for metallization? • It is a good conductor. • it is easy to deposit aluminium films using vacuum deposition. • It makes good mechanical bonds with silicon. • It forms a low resistance . 8. What are the popular IC packages available? • Metal can package. • Dual-in-line package. • Ceramic flat package. 9. Write the basic chemical reaction in the epitaxial growth process of pure silicon. The basic chemical reaction in the epitaxial growth process of pure silicon is the hydrogen reduction of silicon tetrachloride. 1200oC SiCl4 + 2H2 < ------------ > Si + 4 HCl
VVCET – Dept. of ECE
Linear Integrated Circuits
10.Explain the process of oxidation. The silicon wafers are stacked up in a quartz boat & then inserted into quartz furnace tube. The Si wafers are raised to a high temperature in the range of 950 to 1150oC & at the same time, exposed to a gas containing O2 or H2O or both.The chemical action is Si + 2H2O <--------- > SiO2 + 2H2 11.What is meant by molecular beam epitaxy(MBE)? In the molecular beam epitaxy, silicon along with dopants is evaporated. The evaporated species are transported at a relatively high velocity in a vacuum to the substrate. The relatively low vapor pressure of silicon & the dopants ensures condensation on a low temperature substrate. Usually, silicon MBE is performed under ultra high vacuum (UHV) condition of 10-8 to 10-10 Torr. 12.What is lithography? Lithography is a process by which the pattern appearing on the mask is transferred to the wafer. It involves two steps: the first step requires applying a few drops of photoresist to the surface of the wafer & the second step is spinning the surface to get an even coating of the photoresist across the surface of the wafer. 13.Define diffusion. The process of introducing impurities into selected regions of a silicon wafer is called diffusion. The rate atwhich various impurities diffuse into the silicon will be of the order of 1µm/hr at the temperature range of 900oC to 1100oC .The impurity atoms have the tendency to move from regions of higher concentrations to lower concentrations. 14.What is dielectric isolation? In dielectric isolation, a layer of solid dielectric such as SiO2 or ruby completely surrounds each components thereby producing isolation, both electrical & physical. This isolating dielectric layer is thick enough so that its associated capacitance is negligible. Also, it is possible to fabricate both PNP & NPN transistors within the same silicon substrate. 15.What are the advantages of ion implantation technique? • It is performed at low temperature. Therefore, previously diffused regions have a lesser tendency for lateral spreading. • In diffusion process, temperature has to be controlled over a large area inside the oven, whereas in ion implantation process, accelerating potential & beam content are dielectrically controlled from outside. 16.What is metallization? The process of producing a thin metal film layer that will serve to make interconnection of the various components on the chip is called metallization. 17.What are the different types of lithography? What is optical lithography? • The different types of lithography are: • Photolithography • Electron beam lithography • X ray beam lithography • Ion beam lithography 18.Define an operational amplifier. An operational amplifier is a direct-coupled, high gain amplifier consisting of one or more differential amplifier. By properly selecting the external components, it can be used to perform a variety of mathematical operations. 19.Mention the characteristics of an ideal op-amp. • Open loop voltage gain is infinity. • Input impedance is infinity. • Output impedance is zero. • Bandwidth is infinity. • Zero offset.
VVCET – Dept. of ECE
Linear Integrated Circuits
20.What happens when the common terminal of V+ and V- sources is not grounded? If the common point of the two supplies is not grounded, twice the supply voltage will get applied and it may damage the op-amp. 21.Define input offset voltage. A small voltage applied to the input terminals to make the output voltage as zero when the two input terminals are grounded is called input offset voltage. 22.Define input offset current. State the reasons for the offset currents at the input of the op-amp. The difference between the bias currents at the input terminals of the op-amp is called as input offset current. The input terminals conduct a small value of dc current to bias the input transistors. Since the input transistors cannot be made identical, there exists a difference in bias currents. 23.Define CMRR of an op-amp. The relative sensitivity of an op-amp to a difference signal as compared to a common – mode signal is called the common –mode rejection ratio. It is expressed in decibels. CMRR= Ad/Ac 24.What are the applications of current sources? Transistor current sources are widely used in analog ICs both as biasing elements and as load devices for amplifier stages. 25.Justify the reasons for using current sources in integrated circuits. • superior insensitivity of circuit performance to power supply variations and temperature. • more economical than resistors in of die area required to provide bias currents of small value. • When used as load element, the high incremental resistance of current source results in high voltage gain at low supply voltages. 26.What is the advantage of widlar current source over constant current source? Using constant current source output current of small magnitude (microamp range) is not attainable due to the limitations in chip area. Widlar current source is useful for obtaining small output currents. Sensitivity of widlar current source is less compared to constant current source. 27.Mention the advantages of Wilson current source. • Provides high output resistance. • Offers low sensitivity to transistor base currents. 28.Define sensitivity. Sensitivity is defined as the percentage or fractional change in output current per percentage or fractional change in power-supply voltage. 29.What are the limitations in a temperature compensated zener-reference source? A power supply voltage of atleast 7 to 10 V is required to place the diode in the breakdown region and that substantial noise is introduced in the circuit by the avalanching diode. 30.What do you mean by a band-gap referenced biasing circuit? The biasing sources referenced to VBE has a negative temperature co-efficient and VT has a positive temperature co-efficient. Band gap reference circuit is one in which the output current is referenced to a composite voltage that is a weighted sum of VBE and VT so that by proper weighting, zero temperature co-efficient can be achieved. 31.In practical op-amps, what is the effect of high frequency on its performance? The open-loop gain of op-amp decreases at higher frequencies due to the presence of parasitic capacitance. The closed-loop gain increases at higher frequencies and leads to instability. 32.What is the need for frequency compensation in practical op-amps? Frequency compensation is needed when large bandwidth and lower closed loop gain is desired. Compensating networks are used to control the phase shift and hence to improve the stability. VVCET – Dept. of ECE
Linear Integrated Circuits
33.Mention the frequency compensation methods. • Dominant-pole compensation • Pole-zero compensation. 34.What are the merits and demerits of Dominant-pole compensation? • noise immunity of the system is improved. • Open-loop bandwidth is reduced. 35.Define slew rate. The slew rate is defined as the maximum rate of change of output voltage caused by a step input voltage. An ideal slew rate is infinite which means that op-amp’s output voltage should change instantaneously in response to input step voltage. 36.Define thermal drift. The bias current, offset current & offset voltage change with temperature. A circuit carefully nulled at 25oC may not remain so when the temperature raises to 35oC.This is called thermal drift. Often, offset current drift is expressed in nA/ oC and offset voltage drift in mV/ oC. 37.Define supply voltage rejection ratio (SVRR) The change in OPAMP’s input offset voltage due to variations in supply voltage is called the supply voltage rejection ratio. It is also called Power Supply Rejection Ratio (PSRR) or Power Supply Sensitivity (PSS). 38.Why IC 741 is not used for high frequency applications? IC741 has a low slew rate because of the predominance of capacitance present in the circuit at higher frequencies. As frequency increases the output gets distorted due to limited slew rate. 39.What causes slew rate? There is a capacitor with-in or outside of an op-amp to prevent oscillation.It is this capacitor which prevents the output voltage from responding immediately to a fast changing input. 40.What is frequency response of Op-amp? The plot showing the variations in magnitude and phase angle of the gain due to change in frequency is called frequency response of Op-amp. The plot is used to find the bandwidth and cut-off frequencies of Op-amp. 41.What is active load? Where it is used and why? • The current mirror circuit when used as collector load resistance in a differential amplifier is called as an active load. • This circuit provided high value of AC collector resistance which is required to achieve high differential gain but it does not disturb DC conditions of the circuit. 42.Why open loop Op-amp configurations are not used in linear applications? • The open loop gain of the Op-amp is very large. So even for very small variations in the input voltage the output saturates to give the supply voltage as output. • And the linear range of operation is for very small range of input voltage, of the order of few microvolts. So open loop Op-amp configurations are not used for linear applications. 43.What is the use of Buried n+ layer in monolithic IC transistor? • In integrated transistors as collector is at the top, it increases the collector current path, which increases the collector series resistance, hence VCE(sat) of the device. • This higher collector series resistance can be reduced by a process known as buried n+ layer. • In this a heavily doped n+ region is sandwiched between n-type epitaxial collector and p-type substrate. • This buried n+ region provides a low resistivity current path from the active collector region to the collector . • In effect, the n+ layer shunts the n-layer of the collector region w.r.t the flow of current thus effectively reducing the collector resistance.
VVCET – Dept. of ECE
Linear Integrated Circuits
44.Define Sheet resistance. Consider the square L x L of a material of resistivity ρ, thickness t, and cross-sectional area A = L x t. The resistance of this sheet of material can be written as, Rs =
=
45.Define Unity Gain Bandwidth of Op-amp. For a certain frequency of the input signal, the gain of the Op-amp reduces to 0 dB. This means 20 log |AOL (f) | is 0dB i.e. |AOL (f) | = 1. Such a frequency is called gain cross over frequency or unity gain bandwidth (UGB). UNIT II: APPLICATIONS OF OP – AMPS 1. Mention some of the linear applications of op – amps : Adder, subtractor, voltage –to- current converter, current –to- voltage converters, instrumentation amplifier, analog computation, power amplifier, etc are some of the linear opamp circuits. 2. Mention some of the non – linear applications of op-amps:Rectifier, peak detector, clipper, clamper, sample and hold circuit, log amplifier, anti –log amplifier, multiplier are some of the non – linear op-amp circuits. 3. What are the assumptions made from ideal opamp characteristics? • The current drawn by either of the input terminals (noninverting / inverting) is negligible. • The potential difference between the inverting & non-inverting input terminals is zero. 4. What are the areas of application of non-linear op- amp circuits? • Industrial instrumentation • Communication • Signal processing 5. What is the need for an instrumentation amplifier? In a number of industrial and consumer applications, the measurement of physical quantities is usually done with the help of transducers. The output of transducer has to be amplified So that it can drive the indicator or display system. This function is performed by an instrumentation amplifier. 6. List the features of instrumentation amplifier: • high gain accuracy • high CMRR • high gain stability with low temperature co-efficient • low dc offset • low output impedance 7. What are the applications of V-I converter? • Low voltage dc and ac voltmeter • LED • Zener diode tester 8. What do you mean by a precision diode? The major limitation of ordinary diode is that it cannot rectify voltages below the cut – in voltage of the diode. A circuit designed by placing a diode in the loop of an op – amp is called the precision diode and it is capable of rectifying input signals of the order of millivolt. 9. Write down the applications of precision diode. • Half - wave rectifier • Full - Wave rectifier • Peak – value detector • Clipper • Clamper
VVCET – Dept. of ECE
Linear Integrated Circuits
10.List the applications of Log amplifiers: • Analog computation may require functions such as lnx, log x, sin hx etc. These functions can be performed by log amplifiers • Log amplifier can perform direct dB display on digital voltmeter and spectrum analyzer • Log amplifier can be used to compress the dynamic range of a signal 11.What are the limitations of the basic differentiator circuit? At high frequency, a differentiator may become unstable and break into oscillations The input impedance decreases with increase in frequency, thereby making the circuit sensitive to high frequency noise. 12.Write down the condition for good differentiation:For good differentiation, the time period of the input signal must be greater than or equal to Rf C1 T > R f C1 Where, Rf is the resistance Cf is the input capacitance 13.What is a comparator? A comparator is a circuit which compares a signal voltage applied at one input of an op-amp with a known reference voltage at the other input. It is an open loop op - amp with output + Vsat . 14.What are the applications of comparator? • Zero crossing detectors • Window detector • Time marker generator • Phase detector 15.What is a Schmitt trigger? Schmitt trigger is a regenerative comparator. It converts sinusoidal input into a square wave output. The output of Schmitt trigger swings between upper and lower threshold voltages, which are the reference voltages of the input waveform. 16.What is a multivibrator? Multivibrators are a group of regenerative circuits that are used extensively in timing applications. It is a wave shaping circuit which gives symmetric or asymmetric square output. It has two states either stable or quasi- stable depending on the type of multivibrator. 17.What do you mean by monostable multivibrator? Monostable multivibrator is one which generates a single pulse of specified duration in response to each external trigger signal. It has only one stable state. Application of a trigger causes a change to the quasi-stable state.An external trigger signal generated due to charging and discharging of the capacitor produces the transition to the original stable state. 18.What is an astable multivibrator? Astable multivibrator is a free running oscillator having two quasi-stable states. Thus, there are oscillations between these two states and no external signal are required to produce the change in state. 19.What is a bistable multivibrator? Bistable multivibrator is one that maintains a given output voltage level unless an external trigger is applied . Application of an external trigger signal causes a change of state, and this output level is maintained indefinitely until an second trigger is applied . Thus, it requires two external triggers before it returns to its initial state 20.What are the requirements for producing sustained oscillations in circuits? For sustained oscillations, • The total phase shift around the loop must be zero at the desired frequency of oscillation, fo. • At fo, the magnitude of the loop gain |βA| should be equal to unity
VVCET – Dept. of ECE
Linear Integrated Circuits
21.Mention any two audio frequency oscillators : • RC phase shift oscillator • Wein bridge oscillator 22.What are the characteristics of a comparator? • Speed of operation • Accuracy • Compatibility of the output 23.What is a filter? Filter is a frequency selective circuit that es signal of specified band of frequencies and attenuates the signals of frequencies outside the band 24.What are the demerits of ive filters? ive filters works well for high frequencies. But at audio frequencies, the inductors become problematic, as they become large, heavy and expensive. For low frequency applications, more number of turns of wire must be used which in turn adds to the series resistance degrading inductor’s performance ie, low Q, resulting in high power dissipation. 25.What are the advantages of active filters? • Active filters used op- amp as the active element and resistors and capacitors as ive elements. • By enclosing a capacitor in the feed back loop , inductor less active filters can be obtained • Op-amp used in non – inverting configuration offers high input impedance and low output impedance, thus improving the load drive capacity. 26.Mention some commonly used active filters : • Low filter • High filter • Band filter • Band reject filter. 27.What is frequency scaling? Once the filter is designed, sometimes it is necessary to change the value of cut-off frequency. The method used to change the original cut-off frequency to new cut-off frequency is called frequency scaling. 28.Define virtual ground property of Op-amp. Concept of virtual ground says that the two input terminals of the Op-amp are always at the same potential. Thus if one terminal is grounded the other can be assumed to be at ground potential, which is called virtual ground. 29.What is Voltage follower? • A circuit in which the output voltage follows the input voltage is called voltage follower circuit. • In Op-amp if the inverting input and the output terminals are shorted and if any signal is applied at the non-inverting terminal, it appears at the output without any change. • It is also called as source follower, unity gain amplifier, buffer amplifier or isolation amplifier. 30.Define logarithmic and antilogarithmic amplifier. • The Op-amp circuit in which the output is proportional to the logarithmic of the input is called logarithmic amplifier. It employs a diode or a transistor in the negative path. • The Op-amp circuit in which the output is proportional to the antilogarithmic of the input is called logarithmic amplifier. It employs a diode or a transistor in the input stage. 31.Define band filter. A band filter is basically a frequency selector. It allows one particular band of frequencies to . Thus, the band is between the two cut-off frequencies fH and fL where fH > fL. Any frequency outside this band gets attenuated.
VVCET – Dept. of ECE
Linear Integrated Circuits
32.Differentiate Schmitt trigger and comparator. S.No Comparator is not used that is Op-amp is used in 1. open loop mode False triggering due to noise voltages is 2. possible. A single reference voltage exists which acts as 3. triggering voltage.i.e. Vref or -Vref 4.
The hysteresis exists with a width H=VUT - VLT
Schmitt trigger is used that is Op-amp is used in closed loop mode False triggering due to noise voltages is not possible. Two different threshold voltages exists as VUT and VLT The hysteresis does not exists
UNIT – 3: ANALOG MULTIPLIER AND PLL 1. Define VCO. A voltage controlled oscillator is an oscillator circuit in which the frequency of oscillations can be controlled by an externally applied voltage. 2. List the features of 566 VCO. • Wide supply voltage range(10-24V) • Very linear modulation characteristics • High temperature stability 3. Mention some areas where PLL is widely used: • Radar synchronisation • satellite communication systems • air borne navigational systems • FM communication systems 4. List the basic building blocks of PLL: • Phase detector/comparator • Low filter • Error amplifier • Voltage controlled oscillator 5. What are the three stages through which PLL operates? • Free running • Capture • Locked/ tracking 6. Define lock-in range of a PLL: The range of frequencies over which the PLL can maintain lock with the incoming signal is called the lock-in range or tracking range.It is expressed as a percentage of the VCO free running frequency. 7. Define capture range of PLL: The range of frequencies over which the PLL can acquire lock with an input signal is called the capture range. It is expressed as a percentage of the VCO free running frequency. 8. Define Pull-in time. The total time taken by the PLL to establish lock is called pull-in time. It depends on the initial phase and frequency difference between the two signals as well as on the overall loop gain and loop filter characteristics. 9. For perfect lock, what should be the phase relation between the incoming signal and VCO output signal? The VCO output should be 90 degrees out of phase with respect to the input signal. 10.Give the classification of phase detector: • Analog phase detector • Digital phase detector
VVCET – Dept. of ECE
Linear Integrated Circuits
11.What is a switch type phase detector? An electronic switch is opened and closed by signal coming from VCO and the input signal is chopped at a repetition rate determined by the VCO frequency.This type of phase detector is called a half wave detector since the phase information for only one half of the input signal is detected and averaged. 12.What is a voltage controlled oscillator? Voltage controlled oscillator is a free running multivibrator operating at a set frequency called the free running frequency.This frequency can be shifted to either side by applying a dc control voltage and the frequency deviation is proportional to the dc control voltage. 13.On what parameters does the free running frequency of VCO depend on? • External timing resistor,RT • External timing capacitor,CT • The dc control voltage Vc. • 14.Give the expression for the VCO free running frequency. fo = 0.25 / RT CT 15.What is the purpose of having a low filter in PLL? It removes the high frequency components and noise. Controls the dynamic characteristics of the PLL such as capture range, lock-in range,band-width and transient response. The charge on the filter capacitor gives a short- time memory to the PLL. 16.Discuss the effect of having large capture range. The PLL cannot acquire a signal outside the capture range, but once captured, it will hold on till the frequency goes beyond the lock-in range.Thus , to increase the ability of lock range,large capture range is required.But, a large capture range will make the PLL more susceptible to noise and undesirable signal. 17.Mention some typical applications of PLL: • Frequency multiplication/division • Frequency translation • AM detection • FM demodulation • FSK demodulation. • 18.What are the two types of analog multiplier Ics? • IC AD 533 • IC AD 534 19.What is ICAD 533? It is a multiplier IC by analog devices. It is a low cost IC comprising a transconductance multiplying element, stable reference and an output amplifier. 20.List the features of ICAD533. • Its operation is very simple. • Only 4 external adjustments are necessary • Maximum 4 quadrant error is below 0.5% 21.What is ICAD 534? It is a multiplier IC by analog devices. It is the first general purpose multiplier capable of providing gain upto X100. 22.List the features of ICAD534. • Adjustable scale factor • Low noise • Excellent long time stability 23.List the few applications of ICAD534. • Multiplier • Divider • High quality signal processing VVCET – Dept. of ECE
Linear Integrated Circuits
24.What is a compander IC? Give some examples. The term companding means compressing and expanding. In a communication system, the audio signal is compressed in the transmitter and expanded in the receiver. Examples: LM 2704- LM 2707 ; NE 570/571. 25.What are the merits of companding? • The compression process reduces the dynamic range of the signal before it is transmitted. • Companding preserves the signal to noise ratio of the original signal and avoids non linear distortion of the signal when the input amplitude is large. • It also reduces buzz,bias and low level audio tones caused by mild interference. 26.List the applications of OTA: OTA can be used in • Programmable gain voltage amplifier • Sample and hold circuits • Voltage controlled state variable filter • Current controlled relaxation oscillator. 27.What is a four quadrant multiplier? In a multiplier circuit, if both the inputs are allowed to swing in both positive and negative directions the multiplier is called as a four quadrant multiplier. 28.What is analog multiplier? An analog multiplier is a circuit in which the output is proportional to the multiplication of the two input voltages. It is used in modulation, frequency converters and to solve non-linear equations. 29.Differentiate digital and analog PLLs. Depending on the type of phase detector used, the PLL is classified as digital and analog PLLs. • Analog phase detectors Switch type phase detector Balanced modulator type phase detector • Digital Phase detector Using XOR gate Using RS flip-flop 30.Define FSK modulation. In digital data communication, binary data is transmitted by means of a carrier frequency. FSK employs two different carrier frequencies one for logic 1 and other for logic 0 states of binary data signal. This process is called FSK modulation. 31.Define free running mode. In a PLL if the error control voltage is zero then the PLL is said to be operated in free running mode and its output frequency is called its center frequency f0. UNIT IV – A/D AND D/A CONVERTERS 1. List the broad classification of ADCs. • Direct type ADC. • Integrating type ADC. 2. List out the direct type ADCs. • Flash (comparator) type converter • Counter type converter • Tracking or servo converter • Successive approximation type converter 3. List out some integrating type converters. • Charge balancing ADC • Dual slope ADC VVCET – Dept. of ECE
Linear Integrated Circuits
4. What is integrating type converter? An ADC converter that perform conversion in an indirect manner by first changing the analog I/P signal to a linear function of time or frequency and then to a digital code is known as integrating type A/D converter. 5. Explain in brief the principle of operation of successive Approximation ADC. The circuit of successive approximation ADC consists of a successive approximation (SAR), to find the required value of each bit by trial & error. With the arrival of START command, SAR sets the MSB bit to 1. The O/P is converted into an analog signal & it is compared with I/P signal. This O/P is low or High. This process continues until all bits are checked. 6. What are the main advantages of integrating type ADCs? • The integrating type of ADC’s do not need a sample/Hold circuit at the input. • It is possible to transmit frequency even in noisy environment or in an isolated form. 7. Where are the successive approximation type ADC’s used? The Successive approximation ADCs are used in applications such as data loggers & instrumentation where conversion speed is important. 8. What is the main drawback of a dual-slop ADC? The dual slope ADC has long conversion time. This is the main drawback of dual slope ADC. 9. State the advantages of dual slope ADC: It provides excellent noise rejection of ac signals whose periods are integral multiples of the integration time T. 10.Define conversion time. It is defined as the total time required to convert an analog signal into its digital output. It depends on the conversion technique used & the propagation delay of circuit components. The conversion time of a successive approximation type ADC is given by T = (n+1) where T---clock period Tc---conversion time n----no. of bits 11.Define resolution of a data converter. The resolution of a converter is the smallest change in voltage which may be produced at the output or input of the converter. 12.Resolution (in volts)= VFS/2n-1=1 LSB increment. The resolution of an ADC is defined as the smallest change in anaput for a one bit change at the output. 13.Define accuracy of converter. Absolute accuracy: It is the maximum deviation between the actual converter output & the ideal converter output. Relative accuracy: It is the maximum deviation after gain & offset errors have been removed. The accuracy of a converter is also specified in form of LSB increments or % of full scale voltage. 14.What is settling time? It represents the time it takes for the output to settle within a specified band ±½LSB of its final value following a code change at the input (usually a full scale change). It depends upon the switching time of the logic circuitry due to internal parasitic capacitance & inductances. Settling time ranges from 100ns. 10µs depending on word length & type circuit used.
VVCET – Dept. of ECE
Linear Integrated Circuits
15.Explain in brief stability of a converter: The performance of converter changes with temperature age & power supply variation . So all the relevant parameters such as offset, gain, linearity error & monotonicity must be specified over the full temperature & power supply ranges to have better stability performances. 16.What is meant by linearity? The linearity of an ADC/DAC is an important measure of its accuracy & tells us how close the converter output is to its ideal transfer characteristics. The linearity error is usually expressed as a fraction of LSB increment or percentage of full-scale voltage. A good converter exhibits a linearity error of less than ±½LSB. 17.What is monotonic DAC? A monotonic DAC is one whose analog output increases for an increase in digital input. 18.What is a sample and hold circuit? Where it is used? A sample and hold circuit is one which samples an input signal and holds on to its last sampled value until the input is sampled again. This circuit is mainly used in digital interfacing, analog to digital systems, and pulse code modulation systems. 19.Define sample period and hold period. The time during which the voltage across the capacitor in sample and hold circuit is equal to the input voltage is called sample period.The time period during which the voltage across the capacitor is held constant is called hold period. 20.What is meant by delta modulation? Delta modulation is a technique capable of performing analog signal quantization with smaller bandwidth requirements. Here, the binary output representing the most recent sampled amplitude will be determined on the basis of previous sampled amplitude levels. 21.What is Adaptive delta modulation? If in a delta modulation the delta value is varied according to the rapid change or slowest change in the variation of input signal, then it is called adaptive delta modulation. 22.Find the resolution of an 8-bit DAC. Resolution = 28 = 256 23.Which is the fastest A/D converter and why? `Flash type A/D converter is the fastest ADC, because the fast conversion speed is accomplished by providing 2n-1 comparators and simultaneously comparing the input signal with unique reference levels spaced 1 LSB apart. 24.What are current driven DACs? `The DAC in which the problem of ratioed emitter is solved by using equal value current sinks and exploiting the current scaling capability of the inverted R-2R ladder to obtain binary weighted contributions to the output is known as current driven DAC. 25.What are limitations of Flash type ADC? Flash type ADC employs 2n-1 comparators for conversion which makes it costlier which tradeoffs in the speed of conversion. 26.Name the essentials parts of a DAC. Anaput signal, D/A converter circuit, Switches for DAC. 27.What are advantages and disadvantages of R-2R ladder DAC? Adv:• Easier to build accurately as only two precision metal film resistors are required • Number of bits can be expanded by adding more sections of same R/2R values. • In inverted R/2R ladder DAC, node voltages remain constant with changing input binary words. This avoids any slowdown effects by stray capacitances. Disadv:• With increasing output bits the circuit becomes larger. • The switches used are noted for the sources of errors. VVCET – Dept. of ECE
Linear Integrated Circuits
UNIT V – SPECIAL FUNCTION ICs 1. Mention some applications of 555 timer: • Oscillator • pulse generator • ramp and square wave generator • mono-shot multivibrator • burglar alarm • traffic light control. 2. List the applications of 555 timer in monostable mode of operation: • missing pulse detector • Linear ramp generator • Frequency divider • Pulse width modulation. 3. List the applications of 555 timer in Astable mode of operation: • FSK generator • Pulse-position modulator 4. Define 555 IC? The 555 timer is an integrated circuit specifically designed to perform signal generation and timing functions. 5. List the basic blocks of IC 555 timer? • A relaxation oscillator • RS flip flop • Two comparator • Discharge transistor. 6. List the features of 555 Timer? • It has two basic operating modes: monostable and astble • It is available in three packages. 8 pin metal can , 8 pin dip, 14 pin dip. • It has very high temperature stability. 7. What is a voltage regulator? A voltage regulator is an electronic circuit that provides a stable dc voltage independent of the load current, temperature, and ac line voltage variations. 8. Give the classification of voltage regulators: • Series / Linear regulators • Switching regulators. 9. What is a linear voltage regulator? Series or linear regulator uses a power transistor connected in series between the unregulated dc input and the load and it conducts in the linear region .The output voltage is controlled by the continous voltage drop taking place across the series transistor. 10.What is a switching regulator? Switching regulators are those which operate the power transistor as a high frequency on/off switch, so that the power transistor does not conduct current continously. This gives improved efficiency over series regulators. 11.What are the advantages of IC voltage regulators? • low cost • high reliability • reduction in size • excellent performance 12.Give some examples of monolithic IC voltage regulators: • 78XX series fixed output, positive voltage regulators • 79XX series fixed output, negative voltage regulators • 723 general purpose regulator. VVCET – Dept. of ECE
Linear Integrated Circuits
13.What is the purpose of having input and output capacitors in three terminal IC regulators? A capacitor connected between the input terminal and ground cancels the inductive effects due to long distribution leads. The output capacitor improves the transient response. 14.Define line regulation. Line regulation is defined as the percentage change in the output voltage for a change in the input voltage.It is expressed in millivolts or as a percentage of the output voltage. 15.Define load regulation. Load regulation is defined as the change in output voltage for a change in load current. It is expressed in millivolts or as a percentage of the output voltage. 16.What is meant by current limiting? Current limiting refers to the ability of a regulator to prevent the load current from increasing above a preset value. 17.Give the drawbacks of linear regulators: • The input step down transformer is bulky and expensive because of low line frequency. • Because of low line frequency, large values of filter capacitors are required to decrease the ripple. • Efficiency is reduced due to the continuous power dissipation by the transistor as it operates in the linear region. 18.What is the advantage of switching regulators? • Greater efficiency is achieved as the power transistor is made to operate as low impedance switch.Power transmitted across the transistor is in discrete pulses rather than as a steady current flow. • By using suitable switching loss reduction technique, the switching frequency can be increased so as to reduce the size and weight of the inductors and capacitors. 19.What is an opto-coupler IC? Give examples. • Opto-coupler IC is a combined package of a photo-emitting device and a photosensing device. • Examples for opto-coupler circuit : LED and a photo diode, LED and photo transistor, LED and Darlington. • Examples for opto-coupler IC : MCT 2F , MCT 2E . 20.What are the types of optocouplers? • LED and a photo diode, • LED and photo transistor, • LED and Darlington. 21.Give two examples of IC optocouplers? • Examples for opto-coupler IC • MCT 2F • MCT 2E . 22.Mention the advantages of opto-couplers: • Better isolation between the two stages. • Impedance problem between the stages is eliminated. • Wide frequency response. • Easily interfaced with digital circuit. • Compact and light weight. • Problems such as noise, transients, bounce, are eliminated. 23.What is an isolation amplifier? An isolation amplifier is an amplifier that offers electrical isolation between its input and output terminals.
VVCET – Dept. of ECE
Linear Integrated Circuits
24.What are the features of isolation amplifier? • Easy to use • Ultra low leakage • 18 pin DIP package 25.What is LM380? It is a power amplifier produced by national semiconductor. It is capable of delivering 2.5 W min, to 8 ohm load. 26.What is the need for a tuned amplifier? In radio or TV receivers, it is necessary to select a particular channel among all other available channels. Hence some sort of frequency selective circuit is needed that will allow us to amplify the frequency band required and reject all the other unwanted signals and this function is provided by a tuned amplifier. 27.Give the classification of tuned amplifier: (i) Small signal tuned amplifier *Single tuned *Double tuned *Stagger tuned (ii) Large signal tuned amplifier. 28.List the applications of Isolation amplifier. • Floating pulse amplifier output voltage and current interface. • Instrumentation in high-noise environments. • Analogue front-end processing. • Medical instrumentation. 29.What are the advantages of switched capacitor filters? • Very high value of resistors can be easily simulated using small value capacitors, of the order of 10pF. • The switched capacitor filters require no external reactive components like inductors and capacitors. • Completely active filters can be easily obtained on a monolithic IC chip. • Good temperature stability, high accuracy and low cost. 30.Define drop-out voltage of a fixed voltage regulator. It is the minimum voltage that must exist between input and output terminals. It is defined as the ratio of the r.m.s input ripple voltage to the r.m.s output ripple voltage. It is expressed in decibels (dB). 31.Define video amplifier. A video amplifier has to amplify signals over a wideband of frequencies, say upto 20MHz. It is a RC coupled amplifier with bandwidth from d.c. to high frequency upto few megahertz.
VVCET – Dept. of ECE
Linear Integrated Circuits
Possible Part B Questions:Unit I 1. Fabrication process of Monolithic ICs 2. Realization of discrete circuits in monolithic ICs 3. DC analysis of differential amplifier 4. Differential amplifier with constant current source 5. Differential amplifier active load 6. Wilson current source circuit and widlar current source circuit 7. Band gap voltage reference circuit 8. Internal Stages of Op-amp 9. Methods to improve slew rate 10. AC & DC characteristics of Op-amp 11. Frequency response and stability of Op-amp 12. Internal and External frequency compensation techniques Unit II 1. Need and analysis of Instrumentation amplifier 2. Integrator and differentiator 3. Logarithmic and anti-logarithmic amplifier 4. Schmitt trigger and its applications 5. Precision rectifier and its applications 6. Analysis of low Butterworth filters 7. I to V and V to I converters and applications 8. Clipper and clamper circuits Unit III 1. Gilbert multiplier cell 2. Four quadrant multiplier 3. Analog multiplier using emitter coupled transistor 4. Operation of PLL 5. Operation of VCO 6. Closed loop analysis of PLL 7. Applications of PLL Unit IV 1. Weighted resistor type D/A converter 2. R-2R ladder type D/A converter – Voltage mode and current mode 3. Flash type A/D converter 4. Successive approximation type A/D converter 5. Dual Slope type A/D converter 6. Single slope type A/D converter 7. Sample and Hold circuits for A/D converter Unit V 1. Wien Bridge and RC phase oscillator using IC741 2. Triangular and saw tooth wave generator 3. Working of ICL 8038 function generator 4. Monosatble multivibrator using IC555 5. Astable multivibrator using IC555 6. Working of IC 723 general purpose regulator 7. Short notes on audio amplifier and its applications 8. Short notes on video amplifier 9. Short notes on Isolation amplifier 10. Short notes on Opto-couplers and fiber optic ICs Problems:- (Bakshi book) UNIT I Page no: 2-7, 2-14, 2-22, 3-26, 3-33, 3-34, 3-78 UNIT II Page no: 4-14, 4-23, 4-30, 4-122, 4-159, 5-18, 5-23 UNIT III Page no: 7-37, 7-42 UNIT IV Page no: 8-13, 8-14, 8-15, 8-27, 8-49 UNIT V Page no: 9-8, 9-46, 10-26, 10-38
VVCET – Dept. of ECE
Linear Integrated Circuits
List of ICs to study in our syllabus:LM741 General Purpose Op-amp AD533, AD534 Multiplier ICs NE566 VCO IC NE565 PLL IC LF398 Sample & Hold IC ICL8038 Function Generator IC NE555 Timer IC IC723 Voltage regulator IC78xx Three terminal fixed voltage regulator LM340 series Three terminal voltage regulators LM 317, 337, etc., Three terminal adjustable voltage regulators LM 320 series negative voltage regulators µA 78S40 Switching regulator MF10 Dual Switched capacitor filter LM 380 Audio power amplifier LM 384 Audio power amplifier IC 810 Audio power amplifier TC 9400, 9401, 9402 V to F and F to V converter MC 1550, CA 3040 Video amplifier MCT2E Opto-coupler ISO100 Isolation Amplifier Ideal Vs Practical Characteristics of Op-Amp:S.No 1 2 3 4 5 6 7 8 9 10
Parameter Open loop Voltage gain Output impedance Input impedance Input offset current Input offset voltage Bandwidth CMRR Slew rate Input Bias current Power supply rejection ratio
Symbol AOL Zout Zin Iios Vios BW ρ S Ib PSRR
Ideal ∞ 0 ∞ 0 0 ∞ ∞ ∞ 0 0
Typical for IC 741 2 x 105 75 Ω 2MΩ 20nA 2mV 1 MHz 90 dB 0.5 V/µsec 80nA 30 µV/V
VVCET – Dept. of ECE
LINEAR INTEGRATED CIRCUITS
VVCET – Dept. of ECE
Linear Integrated Circuits
080290022 - LINEAR INTEGRATED CIRCUITS AIM: To teach the basic concepts in the design of electronic circuits using linear integrated circuits and their applications in the processing of analog signals. OBJECTIVES • To introduce the basic building blocks of linear integrated circuits. • To teach the linear and non-linear applications of operational amplifiers. • To introduce the theory and applications of analog multipliers and PLL. • To teach the theory of ADC and DAC • To introduce the concepts of waveform generation and introduce some special function ICs. UNIT - I IC FABRICATION AND CIRCUIT CONFIGURATION FOR LINEAR ICS Advantages of Ics over discrete components – Manufacturing process of monolithic Ics – Construction of monolithic bipolar transistor – Monolithic diodes – Integrated Resistors – Monolithic Capacitors – Inductors. Current mirror and current sources, Current sources as active loads, Voltage sources, Voltage References, BJT Differential amplifier with active loads, General operational amplifier stages -and internal circuit diagrams of IC 741, DC and AC performance characteristics, slew rate, Open and closed loop configurations. UNIT - II APPLICATIONS OF OPERATIONAL AMPLIFIERS Sign Changer, Scale Changer, Phase Shift Circuits, Voltage Follower, V-to-I and I-to-V converters, adder, subtractor, Instrumentation amplifier, Integrator, Differentiator, Logarithmic amplifier, Antilogarithmic amplifier, Comparators, Schmitt trigger, Precision rectifier, peak detector, clipper and clamper, Low-, high- and band- Butterworth filters. UNIT - III ANALOG MULTIPLIER AND PLL Analog Multiplier using Emitter Coupled Transistor Pair - Gilbert Multiplier cell – Variable transconductance technique, analog multiplier ICs and their applications, Operation of the basic PLL, Closed loop analysis, Voltage controlled oscillator, Monolithic PLL IC 565, application of PLL for AM detection, FM detection, FSK modulation and demodulation and Frequency synthesizing. UNIT - IV ANALOG TO DIGITAL AND DIGITAL TO ANALOG CONVERTERS Analog and Digital Data Conversions, D/A converter – specifications - weighted resistor type, R2R Ladder type, Voltage Mode and Current-Mode R-2R Ladder types - switches for D/A converters, high speed sample-and-hold circuits, A/D Converters – specifications - Flash type Successive Approximation type - Single Slope type – Dual Slope type - A/D Converter using Voltage-to-Time Conversion - Over-sampling A/D Converters. UNIT - V WAVEFORM GENERATORS AND SPECIAL FUNCTION ICs Sine-wave generators, Multivibrators and Triangular wave generator, Saw-tooth wave generator, ICL8038 function generator, Timer IC 555, IC Voltage regulators – Three terminal fixed and adjustable voltage regulators - IC 723 general purpose regulator – Monolithic switching regulator, Switched capacitor filter IC MF10, Frequency to Voltage and Voltage to Frequency converters, Audio Power amplifier, Video Amplifier, Isolation Amplifier, Opto-couplers and fibre optic IC. TEXT BOOKS: 1. Sergio Franco, Design with operational amplifiers and anategrated circuits, 3rd Edition, Tata McGraw-Hill, 2007. 2. D.Roy Choudhry, Shail Jain, Linear Integrated Circuits, New Age International Pvt. Ltd., 2000. REFERENCES: 1. B.S.Sonde, System design using Integrated Circuits , New Age Pub, 2nd Edition, 2001 2. Gray and Meyer, Analysis and Design of Anategrated Circuits, Wiley International, 2005. 3. Ramakant A.Gayakwad, OP-AMP and Linear ICs, Prentice Hall / Pearson Education, 4th Edition, 2001. 4. J.Michael Jacob, Applications and Design with Anategrated Circuits, Prentice Hall of India, 1996. 5. William D.Stanley, Operational Amplifiers with Linear Integrated Circuits, Pearson Education, 2004. 6. K Lal Kishore, Operational Amplifier and Linear Integrated Circuits, Pearson Education, 2006. 7. S.Salivahanan & V.S. Kanchana Bhaskaran, Linear Integrated Circuits, TMH, 2008.
VVCET – Dept. of ECE
Linear Integrated Circuits
UNIT-I CIRCUIT CONFIGURATION FOR LINEAR ICs 1. Define an Integrated circuit. An integrated circuit(IC) is a miniature, low cost electronic circuit consisting of active and ive components fabricated together on a single crystal of silicon. The active components are transistors and diodes and ive components are resistors and capacitors. 2. Mention the advantages of integrated circuits. • Miniaturisation and hence increased equipment density. • Cost reduction due to batch processing. • Increased system reliability due to the elimination of soldered ts. • Improved functional performance doe to Matched devices. • Increased operating speeds. • Reduction in power consumption. 3. Write down the various processes used to fabricate IC’s using silicon planar technology. • Silicon wafer preparation. • Epitaxial growth • Oxidation. • Photolithography. • Diffusion. • Ion implantation. • Isolation. • Metallisation. • Assembly processing and packaging. 4. List out the steps used in the preparation of Si – wafers. • Crystal growth &doping • Ingot trimming & grinding • Ingot slicing • Wafer policing & etching • Wafer cleaning 5. What is the purpose of oxidation? • SiO2 is an extremely hard protective coating and is unaffected by almost all reagents. • By selective etching of SiO2, diffusion of impurities through carefully defined windows can be accomplished to fabricate various components. 6. What are the two important properties of SiO2? • SiO2 is an extremely hard protective coatng & is unaffected by almost all reagents except by hydrochloric acid. Thus it stands against any contamination. • By selective etching of SiO2 , diffusion of impurities through carefully defined windows in the SiO2 can be accomplished to fabricate various components. 7. Why aluminium is preferred for metallization? • It is a good conductor. • it is easy to deposit aluminium films using vacuum deposition. • It makes good mechanical bonds with silicon. • It forms a low resistance . 8. What are the popular IC packages available? • Metal can package. • Dual-in-line package. • Ceramic flat package. 9. Write the basic chemical reaction in the epitaxial growth process of pure silicon. The basic chemical reaction in the epitaxial growth process of pure silicon is the hydrogen reduction of silicon tetrachloride. 1200oC SiCl4 + 2H2 < ------------ > Si + 4 HCl
VVCET – Dept. of ECE
Linear Integrated Circuits
10.Explain the process of oxidation. The silicon wafers are stacked up in a quartz boat & then inserted into quartz furnace tube. The Si wafers are raised to a high temperature in the range of 950 to 1150oC & at the same time, exposed to a gas containing O2 or H2O or both.The chemical action is Si + 2H2O <--------- > SiO2 + 2H2 11.What is meant by molecular beam epitaxy(MBE)? In the molecular beam epitaxy, silicon along with dopants is evaporated. The evaporated species are transported at a relatively high velocity in a vacuum to the substrate. The relatively low vapor pressure of silicon & the dopants ensures condensation on a low temperature substrate. Usually, silicon MBE is performed under ultra high vacuum (UHV) condition of 10-8 to 10-10 Torr. 12.What is lithography? Lithography is a process by which the pattern appearing on the mask is transferred to the wafer. It involves two steps: the first step requires applying a few drops of photoresist to the surface of the wafer & the second step is spinning the surface to get an even coating of the photoresist across the surface of the wafer. 13.Define diffusion. The process of introducing impurities into selected regions of a silicon wafer is called diffusion. The rate atwhich various impurities diffuse into the silicon will be of the order of 1µm/hr at the temperature range of 900oC to 1100oC .The impurity atoms have the tendency to move from regions of higher concentrations to lower concentrations. 14.What is dielectric isolation? In dielectric isolation, a layer of solid dielectric such as SiO2 or ruby completely surrounds each components thereby producing isolation, both electrical & physical. This isolating dielectric layer is thick enough so that its associated capacitance is negligible. Also, it is possible to fabricate both PNP & NPN transistors within the same silicon substrate. 15.What are the advantages of ion implantation technique? • It is performed at low temperature. Therefore, previously diffused regions have a lesser tendency for lateral spreading. • In diffusion process, temperature has to be controlled over a large area inside the oven, whereas in ion implantation process, accelerating potential & beam content are dielectrically controlled from outside. 16.What is metallization? The process of producing a thin metal film layer that will serve to make interconnection of the various components on the chip is called metallization. 17.What are the different types of lithography? What is optical lithography? • The different types of lithography are: • Photolithography • Electron beam lithography • X ray beam lithography • Ion beam lithography 18.Define an operational amplifier. An operational amplifier is a direct-coupled, high gain amplifier consisting of one or more differential amplifier. By properly selecting the external components, it can be used to perform a variety of mathematical operations. 19.Mention the characteristics of an ideal op-amp. • Open loop voltage gain is infinity. • Input impedance is infinity. • Output impedance is zero. • Bandwidth is infinity. • Zero offset.
VVCET – Dept. of ECE
Linear Integrated Circuits
20.What happens when the common terminal of V+ and V- sources is not grounded? If the common point of the two supplies is not grounded, twice the supply voltage will get applied and it may damage the op-amp. 21.Define input offset voltage. A small voltage applied to the input terminals to make the output voltage as zero when the two input terminals are grounded is called input offset voltage. 22.Define input offset current. State the reasons for the offset currents at the input of the op-amp. The difference between the bias currents at the input terminals of the op-amp is called as input offset current. The input terminals conduct a small value of dc current to bias the input transistors. Since the input transistors cannot be made identical, there exists a difference in bias currents. 23.Define CMRR of an op-amp. The relative sensitivity of an op-amp to a difference signal as compared to a common – mode signal is called the common –mode rejection ratio. It is expressed in decibels. CMRR= Ad/Ac 24.What are the applications of current sources? Transistor current sources are widely used in analog ICs both as biasing elements and as load devices for amplifier stages. 25.Justify the reasons for using current sources in integrated circuits. • superior insensitivity of circuit performance to power supply variations and temperature. • more economical than resistors in of die area required to provide bias currents of small value. • When used as load element, the high incremental resistance of current source results in high voltage gain at low supply voltages. 26.What is the advantage of widlar current source over constant current source? Using constant current source output current of small magnitude (microamp range) is not attainable due to the limitations in chip area. Widlar current source is useful for obtaining small output currents. Sensitivity of widlar current source is less compared to constant current source. 27.Mention the advantages of Wilson current source. • Provides high output resistance. • Offers low sensitivity to transistor base currents. 28.Define sensitivity. Sensitivity is defined as the percentage or fractional change in output current per percentage or fractional change in power-supply voltage. 29.What are the limitations in a temperature compensated zener-reference source? A power supply voltage of atleast 7 to 10 V is required to place the diode in the breakdown region and that substantial noise is introduced in the circuit by the avalanching diode. 30.What do you mean by a band-gap referenced biasing circuit? The biasing sources referenced to VBE has a negative temperature co-efficient and VT has a positive temperature co-efficient. Band gap reference circuit is one in which the output current is referenced to a composite voltage that is a weighted sum of VBE and VT so that by proper weighting, zero temperature co-efficient can be achieved. 31.In practical op-amps, what is the effect of high frequency on its performance? The open-loop gain of op-amp decreases at higher frequencies due to the presence of parasitic capacitance. The closed-loop gain increases at higher frequencies and leads to instability. 32.What is the need for frequency compensation in practical op-amps? Frequency compensation is needed when large bandwidth and lower closed loop gain is desired. Compensating networks are used to control the phase shift and hence to improve the stability. VVCET – Dept. of ECE
Linear Integrated Circuits
33.Mention the frequency compensation methods. • Dominant-pole compensation • Pole-zero compensation. 34.What are the merits and demerits of Dominant-pole compensation? • noise immunity of the system is improved. • Open-loop bandwidth is reduced. 35.Define slew rate. The slew rate is defined as the maximum rate of change of output voltage caused by a step input voltage. An ideal slew rate is infinite which means that op-amp’s output voltage should change instantaneously in response to input step voltage. 36.Define thermal drift. The bias current, offset current & offset voltage change with temperature. A circuit carefully nulled at 25oC may not remain so when the temperature raises to 35oC.This is called thermal drift. Often, offset current drift is expressed in nA/ oC and offset voltage drift in mV/ oC. 37.Define supply voltage rejection ratio (SVRR) The change in OPAMP’s input offset voltage due to variations in supply voltage is called the supply voltage rejection ratio. It is also called Power Supply Rejection Ratio (PSRR) or Power Supply Sensitivity (PSS). 38.Why IC 741 is not used for high frequency applications? IC741 has a low slew rate because of the predominance of capacitance present in the circuit at higher frequencies. As frequency increases the output gets distorted due to limited slew rate. 39.What causes slew rate? There is a capacitor with-in or outside of an op-amp to prevent oscillation.It is this capacitor which prevents the output voltage from responding immediately to a fast changing input. 40.What is frequency response of Op-amp? The plot showing the variations in magnitude and phase angle of the gain due to change in frequency is called frequency response of Op-amp. The plot is used to find the bandwidth and cut-off frequencies of Op-amp. 41.What is active load? Where it is used and why? • The current mirror circuit when used as collector load resistance in a differential amplifier is called as an active load. • This circuit provided high value of AC collector resistance which is required to achieve high differential gain but it does not disturb DC conditions of the circuit. 42.Why open loop Op-amp configurations are not used in linear applications? • The open loop gain of the Op-amp is very large. So even for very small variations in the input voltage the output saturates to give the supply voltage as output. • And the linear range of operation is for very small range of input voltage, of the order of few microvolts. So open loop Op-amp configurations are not used for linear applications. 43.What is the use of Buried n+ layer in monolithic IC transistor? • In integrated transistors as collector is at the top, it increases the collector current path, which increases the collector series resistance, hence VCE(sat) of the device. • This higher collector series resistance can be reduced by a process known as buried n+ layer. • In this a heavily doped n+ region is sandwiched between n-type epitaxial collector and p-type substrate. • This buried n+ region provides a low resistivity current path from the active collector region to the collector . • In effect, the n+ layer shunts the n-layer of the collector region w.r.t the flow of current thus effectively reducing the collector resistance.
VVCET – Dept. of ECE
Linear Integrated Circuits
44.Define Sheet resistance. Consider the square L x L of a material of resistivity ρ, thickness t, and cross-sectional area A = L x t. The resistance of this sheet of material can be written as, Rs =
=
45.Define Unity Gain Bandwidth of Op-amp. For a certain frequency of the input signal, the gain of the Op-amp reduces to 0 dB. This means 20 log |AOL (f) | is 0dB i.e. |AOL (f) | = 1. Such a frequency is called gain cross over frequency or unity gain bandwidth (UGB). UNIT II: APPLICATIONS OF OP – AMPS 1. Mention some of the linear applications of op – amps : Adder, subtractor, voltage –to- current converter, current –to- voltage converters, instrumentation amplifier, analog computation, power amplifier, etc are some of the linear opamp circuits. 2. Mention some of the non – linear applications of op-amps:Rectifier, peak detector, clipper, clamper, sample and hold circuit, log amplifier, anti –log amplifier, multiplier are some of the non – linear op-amp circuits. 3. What are the assumptions made from ideal opamp characteristics? • The current drawn by either of the input terminals (noninverting / inverting) is negligible. • The potential difference between the inverting & non-inverting input terminals is zero. 4. What are the areas of application of non-linear op- amp circuits? • Industrial instrumentation • Communication • Signal processing 5. What is the need for an instrumentation amplifier? In a number of industrial and consumer applications, the measurement of physical quantities is usually done with the help of transducers. The output of transducer has to be amplified So that it can drive the indicator or display system. This function is performed by an instrumentation amplifier. 6. List the features of instrumentation amplifier: • high gain accuracy • high CMRR • high gain stability with low temperature co-efficient • low dc offset • low output impedance 7. What are the applications of V-I converter? • Low voltage dc and ac voltmeter • LED • Zener diode tester 8. What do you mean by a precision diode? The major limitation of ordinary diode is that it cannot rectify voltages below the cut – in voltage of the diode. A circuit designed by placing a diode in the loop of an op – amp is called the precision diode and it is capable of rectifying input signals of the order of millivolt. 9. Write down the applications of precision diode. • Half - wave rectifier • Full - Wave rectifier • Peak – value detector • Clipper • Clamper
VVCET – Dept. of ECE
Linear Integrated Circuits
10.List the applications of Log amplifiers: • Analog computation may require functions such as lnx, log x, sin hx etc. These functions can be performed by log amplifiers • Log amplifier can perform direct dB display on digital voltmeter and spectrum analyzer • Log amplifier can be used to compress the dynamic range of a signal 11.What are the limitations of the basic differentiator circuit? At high frequency, a differentiator may become unstable and break into oscillations The input impedance decreases with increase in frequency, thereby making the circuit sensitive to high frequency noise. 12.Write down the condition for good differentiation:For good differentiation, the time period of the input signal must be greater than or equal to Rf C1 T > R f C1 Where, Rf is the resistance Cf is the input capacitance 13.What is a comparator? A comparator is a circuit which compares a signal voltage applied at one input of an op-amp with a known reference voltage at the other input. It is an open loop op - amp with output + Vsat . 14.What are the applications of comparator? • Zero crossing detectors • Window detector • Time marker generator • Phase detector 15.What is a Schmitt trigger? Schmitt trigger is a regenerative comparator. It converts sinusoidal input into a square wave output. The output of Schmitt trigger swings between upper and lower threshold voltages, which are the reference voltages of the input waveform. 16.What is a multivibrator? Multivibrators are a group of regenerative circuits that are used extensively in timing applications. It is a wave shaping circuit which gives symmetric or asymmetric square output. It has two states either stable or quasi- stable depending on the type of multivibrator. 17.What do you mean by monostable multivibrator? Monostable multivibrator is one which generates a single pulse of specified duration in response to each external trigger signal. It has only one stable state. Application of a trigger causes a change to the quasi-stable state.An external trigger signal generated due to charging and discharging of the capacitor produces the transition to the original stable state. 18.What is an astable multivibrator? Astable multivibrator is a free running oscillator having two quasi-stable states. Thus, there are oscillations between these two states and no external signal are required to produce the change in state. 19.What is a bistable multivibrator? Bistable multivibrator is one that maintains a given output voltage level unless an external trigger is applied . Application of an external trigger signal causes a change of state, and this output level is maintained indefinitely until an second trigger is applied . Thus, it requires two external triggers before it returns to its initial state 20.What are the requirements for producing sustained oscillations in circuits? For sustained oscillations, • The total phase shift around the loop must be zero at the desired frequency of oscillation, fo. • At fo, the magnitude of the loop gain |βA| should be equal to unity
VVCET – Dept. of ECE
Linear Integrated Circuits
21.Mention any two audio frequency oscillators : • RC phase shift oscillator • Wein bridge oscillator 22.What are the characteristics of a comparator? • Speed of operation • Accuracy • Compatibility of the output 23.What is a filter? Filter is a frequency selective circuit that es signal of specified band of frequencies and attenuates the signals of frequencies outside the band 24.What are the demerits of ive filters? ive filters works well for high frequencies. But at audio frequencies, the inductors become problematic, as they become large, heavy and expensive. For low frequency applications, more number of turns of wire must be used which in turn adds to the series resistance degrading inductor’s performance ie, low Q, resulting in high power dissipation. 25.What are the advantages of active filters? • Active filters used op- amp as the active element and resistors and capacitors as ive elements. • By enclosing a capacitor in the feed back loop , inductor less active filters can be obtained • Op-amp used in non – inverting configuration offers high input impedance and low output impedance, thus improving the load drive capacity. 26.Mention some commonly used active filters : • Low filter • High filter • Band filter • Band reject filter. 27.What is frequency scaling? Once the filter is designed, sometimes it is necessary to change the value of cut-off frequency. The method used to change the original cut-off frequency to new cut-off frequency is called frequency scaling. 28.Define virtual ground property of Op-amp. Concept of virtual ground says that the two input terminals of the Op-amp are always at the same potential. Thus if one terminal is grounded the other can be assumed to be at ground potential, which is called virtual ground. 29.What is Voltage follower? • A circuit in which the output voltage follows the input voltage is called voltage follower circuit. • In Op-amp if the inverting input and the output terminals are shorted and if any signal is applied at the non-inverting terminal, it appears at the output without any change. • It is also called as source follower, unity gain amplifier, buffer amplifier or isolation amplifier. 30.Define logarithmic and antilogarithmic amplifier. • The Op-amp circuit in which the output is proportional to the logarithmic of the input is called logarithmic amplifier. It employs a diode or a transistor in the negative path. • The Op-amp circuit in which the output is proportional to the antilogarithmic of the input is called logarithmic amplifier. It employs a diode or a transistor in the input stage. 31.Define band filter. A band filter is basically a frequency selector. It allows one particular band of frequencies to . Thus, the band is between the two cut-off frequencies fH and fL where fH > fL. Any frequency outside this band gets attenuated.
VVCET – Dept. of ECE
Linear Integrated Circuits
32.Differentiate Schmitt trigger and comparator. S.No Comparator is not used that is Op-amp is used in 1. open loop mode False triggering due to noise voltages is 2. possible. A single reference voltage exists which acts as 3. triggering voltage.i.e. Vref or -Vref 4.
The hysteresis exists with a width H=VUT - VLT
Schmitt trigger is used that is Op-amp is used in closed loop mode False triggering due to noise voltages is not possible. Two different threshold voltages exists as VUT and VLT The hysteresis does not exists
UNIT – 3: ANALOG MULTIPLIER AND PLL 1. Define VCO. A voltage controlled oscillator is an oscillator circuit in which the frequency of oscillations can be controlled by an externally applied voltage. 2. List the features of 566 VCO. • Wide supply voltage range(10-24V) • Very linear modulation characteristics • High temperature stability 3. Mention some areas where PLL is widely used: • Radar synchronisation • satellite communication systems • air borne navigational systems • FM communication systems 4. List the basic building blocks of PLL: • Phase detector/comparator • Low filter • Error amplifier • Voltage controlled oscillator 5. What are the three stages through which PLL operates? • Free running • Capture • Locked/ tracking 6. Define lock-in range of a PLL: The range of frequencies over which the PLL can maintain lock with the incoming signal is called the lock-in range or tracking range.It is expressed as a percentage of the VCO free running frequency. 7. Define capture range of PLL: The range of frequencies over which the PLL can acquire lock with an input signal is called the capture range. It is expressed as a percentage of the VCO free running frequency. 8. Define Pull-in time. The total time taken by the PLL to establish lock is called pull-in time. It depends on the initial phase and frequency difference between the two signals as well as on the overall loop gain and loop filter characteristics. 9. For perfect lock, what should be the phase relation between the incoming signal and VCO output signal? The VCO output should be 90 degrees out of phase with respect to the input signal. 10.Give the classification of phase detector: • Analog phase detector • Digital phase detector
VVCET – Dept. of ECE
Linear Integrated Circuits
11.What is a switch type phase detector? An electronic switch is opened and closed by signal coming from VCO and the input signal is chopped at a repetition rate determined by the VCO frequency.This type of phase detector is called a half wave detector since the phase information for only one half of the input signal is detected and averaged. 12.What is a voltage controlled oscillator? Voltage controlled oscillator is a free running multivibrator operating at a set frequency called the free running frequency.This frequency can be shifted to either side by applying a dc control voltage and the frequency deviation is proportional to the dc control voltage. 13.On what parameters does the free running frequency of VCO depend on? • External timing resistor,RT • External timing capacitor,CT • The dc control voltage Vc. • 14.Give the expression for the VCO free running frequency. fo = 0.25 / RT CT 15.What is the purpose of having a low filter in PLL? It removes the high frequency components and noise. Controls the dynamic characteristics of the PLL such as capture range, lock-in range,band-width and transient response. The charge on the filter capacitor gives a short- time memory to the PLL. 16.Discuss the effect of having large capture range. The PLL cannot acquire a signal outside the capture range, but once captured, it will hold on till the frequency goes beyond the lock-in range.Thus , to increase the ability of lock range,large capture range is required.But, a large capture range will make the PLL more susceptible to noise and undesirable signal. 17.Mention some typical applications of PLL: • Frequency multiplication/division • Frequency translation • AM detection • FM demodulation • FSK demodulation. • 18.What are the two types of analog multiplier Ics? • IC AD 533 • IC AD 534 19.What is ICAD 533? It is a multiplier IC by analog devices. It is a low cost IC comprising a transconductance multiplying element, stable reference and an output amplifier. 20.List the features of ICAD533. • Its operation is very simple. • Only 4 external adjustments are necessary • Maximum 4 quadrant error is below 0.5% 21.What is ICAD 534? It is a multiplier IC by analog devices. It is the first general purpose multiplier capable of providing gain upto X100. 22.List the features of ICAD534. • Adjustable scale factor • Low noise • Excellent long time stability 23.List the few applications of ICAD534. • Multiplier • Divider • High quality signal processing VVCET – Dept. of ECE
Linear Integrated Circuits
24.What is a compander IC? Give some examples. The term companding means compressing and expanding. In a communication system, the audio signal is compressed in the transmitter and expanded in the receiver. Examples: LM 2704- LM 2707 ; NE 570/571. 25.What are the merits of companding? • The compression process reduces the dynamic range of the signal before it is transmitted. • Companding preserves the signal to noise ratio of the original signal and avoids non linear distortion of the signal when the input amplitude is large. • It also reduces buzz,bias and low level audio tones caused by mild interference. 26.List the applications of OTA: OTA can be used in • Programmable gain voltage amplifier • Sample and hold circuits • Voltage controlled state variable filter • Current controlled relaxation oscillator. 27.What is a four quadrant multiplier? In a multiplier circuit, if both the inputs are allowed to swing in both positive and negative directions the multiplier is called as a four quadrant multiplier. 28.What is analog multiplier? An analog multiplier is a circuit in which the output is proportional to the multiplication of the two input voltages. It is used in modulation, frequency converters and to solve non-linear equations. 29.Differentiate digital and analog PLLs. Depending on the type of phase detector used, the PLL is classified as digital and analog PLLs. • Analog phase detectors Switch type phase detector Balanced modulator type phase detector • Digital Phase detector Using XOR gate Using RS flip-flop 30.Define FSK modulation. In digital data communication, binary data is transmitted by means of a carrier frequency. FSK employs two different carrier frequencies one for logic 1 and other for logic 0 states of binary data signal. This process is called FSK modulation. 31.Define free running mode. In a PLL if the error control voltage is zero then the PLL is said to be operated in free running mode and its output frequency is called its center frequency f0. UNIT IV – A/D AND D/A CONVERTERS 1. List the broad classification of ADCs. • Direct type ADC. • Integrating type ADC. 2. List out the direct type ADCs. • Flash (comparator) type converter • Counter type converter • Tracking or servo converter • Successive approximation type converter 3. List out some integrating type converters. • Charge balancing ADC • Dual slope ADC VVCET – Dept. of ECE
Linear Integrated Circuits
4. What is integrating type converter? An ADC converter that perform conversion in an indirect manner by first changing the analog I/P signal to a linear function of time or frequency and then to a digital code is known as integrating type A/D converter. 5. Explain in brief the principle of operation of successive Approximation ADC. The circuit of successive approximation ADC consists of a successive approximation (SAR), to find the required value of each bit by trial & error. With the arrival of START command, SAR sets the MSB bit to 1. The O/P is converted into an analog signal & it is compared with I/P signal. This O/P is low or High. This process continues until all bits are checked. 6. What are the main advantages of integrating type ADCs? • The integrating type of ADC’s do not need a sample/Hold circuit at the input. • It is possible to transmit frequency even in noisy environment or in an isolated form. 7. Where are the successive approximation type ADC’s used? The Successive approximation ADCs are used in applications such as data loggers & instrumentation where conversion speed is important. 8. What is the main drawback of a dual-slop ADC? The dual slope ADC has long conversion time. This is the main drawback of dual slope ADC. 9. State the advantages of dual slope ADC: It provides excellent noise rejection of ac signals whose periods are integral multiples of the integration time T. 10.Define conversion time. It is defined as the total time required to convert an analog signal into its digital output. It depends on the conversion technique used & the propagation delay of circuit components. The conversion time of a successive approximation type ADC is given by T = (n+1) where T---clock period Tc---conversion time n----no. of bits 11.Define resolution of a data converter. The resolution of a converter is the smallest change in voltage which may be produced at the output or input of the converter. 12.Resolution (in volts)= VFS/2n-1=1 LSB increment. The resolution of an ADC is defined as the smallest change in anaput for a one bit change at the output. 13.Define accuracy of converter. Absolute accuracy: It is the maximum deviation between the actual converter output & the ideal converter output. Relative accuracy: It is the maximum deviation after gain & offset errors have been removed. The accuracy of a converter is also specified in form of LSB increments or % of full scale voltage. 14.What is settling time? It represents the time it takes for the output to settle within a specified band ±½LSB of its final value following a code change at the input (usually a full scale change). It depends upon the switching time of the logic circuitry due to internal parasitic capacitance & inductances. Settling time ranges from 100ns. 10µs depending on word length & type circuit used.
VVCET – Dept. of ECE
Linear Integrated Circuits
15.Explain in brief stability of a converter: The performance of converter changes with temperature age & power supply variation . So all the relevant parameters such as offset, gain, linearity error & monotonicity must be specified over the full temperature & power supply ranges to have better stability performances. 16.What is meant by linearity? The linearity of an ADC/DAC is an important measure of its accuracy & tells us how close the converter output is to its ideal transfer characteristics. The linearity error is usually expressed as a fraction of LSB increment or percentage of full-scale voltage. A good converter exhibits a linearity error of less than ±½LSB. 17.What is monotonic DAC? A monotonic DAC is one whose analog output increases for an increase in digital input. 18.What is a sample and hold circuit? Where it is used? A sample and hold circuit is one which samples an input signal and holds on to its last sampled value until the input is sampled again. This circuit is mainly used in digital interfacing, analog to digital systems, and pulse code modulation systems. 19.Define sample period and hold period. The time during which the voltage across the capacitor in sample and hold circuit is equal to the input voltage is called sample period.The time period during which the voltage across the capacitor is held constant is called hold period. 20.What is meant by delta modulation? Delta modulation is a technique capable of performing analog signal quantization with smaller bandwidth requirements. Here, the binary output representing the most recent sampled amplitude will be determined on the basis of previous sampled amplitude levels. 21.What is Adaptive delta modulation? If in a delta modulation the delta value is varied according to the rapid change or slowest change in the variation of input signal, then it is called adaptive delta modulation. 22.Find the resolution of an 8-bit DAC. Resolution = 28 = 256 23.Which is the fastest A/D converter and why? `Flash type A/D converter is the fastest ADC, because the fast conversion speed is accomplished by providing 2n-1 comparators and simultaneously comparing the input signal with unique reference levels spaced 1 LSB apart. 24.What are current driven DACs? `The DAC in which the problem of ratioed emitter is solved by using equal value current sinks and exploiting the current scaling capability of the inverted R-2R ladder to obtain binary weighted contributions to the output is known as current driven DAC. 25.What are limitations of Flash type ADC? Flash type ADC employs 2n-1 comparators for conversion which makes it costlier which tradeoffs in the speed of conversion. 26.Name the essentials parts of a DAC. Anaput signal, D/A converter circuit, Switches for DAC. 27.What are advantages and disadvantages of R-2R ladder DAC? Adv:• Easier to build accurately as only two precision metal film resistors are required • Number of bits can be expanded by adding more sections of same R/2R values. • In inverted R/2R ladder DAC, node voltages remain constant with changing input binary words. This avoids any slowdown effects by stray capacitances. Disadv:• With increasing output bits the circuit becomes larger. • The switches used are noted for the sources of errors. VVCET – Dept. of ECE
Linear Integrated Circuits
UNIT V – SPECIAL FUNCTION ICs 1. Mention some applications of 555 timer: • Oscillator • pulse generator • ramp and square wave generator • mono-shot multivibrator • burglar alarm • traffic light control. 2. List the applications of 555 timer in monostable mode of operation: • missing pulse detector • Linear ramp generator • Frequency divider • Pulse width modulation. 3. List the applications of 555 timer in Astable mode of operation: • FSK generator • Pulse-position modulator 4. Define 555 IC? The 555 timer is an integrated circuit specifically designed to perform signal generation and timing functions. 5. List the basic blocks of IC 555 timer? • A relaxation oscillator • RS flip flop • Two comparator • Discharge transistor. 6. List the features of 555 Timer? • It has two basic operating modes: monostable and astble • It is available in three packages. 8 pin metal can , 8 pin dip, 14 pin dip. • It has very high temperature stability. 7. What is a voltage regulator? A voltage regulator is an electronic circuit that provides a stable dc voltage independent of the load current, temperature, and ac line voltage variations. 8. Give the classification of voltage regulators: • Series / Linear regulators • Switching regulators. 9. What is a linear voltage regulator? Series or linear regulator uses a power transistor connected in series between the unregulated dc input and the load and it conducts in the linear region .The output voltage is controlled by the continous voltage drop taking place across the series transistor. 10.What is a switching regulator? Switching regulators are those which operate the power transistor as a high frequency on/off switch, so that the power transistor does not conduct current continously. This gives improved efficiency over series regulators. 11.What are the advantages of IC voltage regulators? • low cost • high reliability • reduction in size • excellent performance 12.Give some examples of monolithic IC voltage regulators: • 78XX series fixed output, positive voltage regulators • 79XX series fixed output, negative voltage regulators • 723 general purpose regulator. VVCET – Dept. of ECE
Linear Integrated Circuits
13.What is the purpose of having input and output capacitors in three terminal IC regulators? A capacitor connected between the input terminal and ground cancels the inductive effects due to long distribution leads. The output capacitor improves the transient response. 14.Define line regulation. Line regulation is defined as the percentage change in the output voltage for a change in the input voltage.It is expressed in millivolts or as a percentage of the output voltage. 15.Define load regulation. Load regulation is defined as the change in output voltage for a change in load current. It is expressed in millivolts or as a percentage of the output voltage. 16.What is meant by current limiting? Current limiting refers to the ability of a regulator to prevent the load current from increasing above a preset value. 17.Give the drawbacks of linear regulators: • The input step down transformer is bulky and expensive because of low line frequency. • Because of low line frequency, large values of filter capacitors are required to decrease the ripple. • Efficiency is reduced due to the continuous power dissipation by the transistor as it operates in the linear region. 18.What is the advantage of switching regulators? • Greater efficiency is achieved as the power transistor is made to operate as low impedance switch.Power transmitted across the transistor is in discrete pulses rather than as a steady current flow. • By using suitable switching loss reduction technique, the switching frequency can be increased so as to reduce the size and weight of the inductors and capacitors. 19.What is an opto-coupler IC? Give examples. • Opto-coupler IC is a combined package of a photo-emitting device and a photosensing device. • Examples for opto-coupler circuit : LED and a photo diode, LED and photo transistor, LED and Darlington. • Examples for opto-coupler IC : MCT 2F , MCT 2E . 20.What are the types of optocouplers? • LED and a photo diode, • LED and photo transistor, • LED and Darlington. 21.Give two examples of IC optocouplers? • Examples for opto-coupler IC • MCT 2F • MCT 2E . 22.Mention the advantages of opto-couplers: • Better isolation between the two stages. • Impedance problem between the stages is eliminated. • Wide frequency response. • Easily interfaced with digital circuit. • Compact and light weight. • Problems such as noise, transients, bounce, are eliminated. 23.What is an isolation amplifier? An isolation amplifier is an amplifier that offers electrical isolation between its input and output terminals.
VVCET – Dept. of ECE
Linear Integrated Circuits
24.What are the features of isolation amplifier? • Easy to use • Ultra low leakage • 18 pin DIP package 25.What is LM380? It is a power amplifier produced by national semiconductor. It is capable of delivering 2.5 W min, to 8 ohm load. 26.What is the need for a tuned amplifier? In radio or TV receivers, it is necessary to select a particular channel among all other available channels. Hence some sort of frequency selective circuit is needed that will allow us to amplify the frequency band required and reject all the other unwanted signals and this function is provided by a tuned amplifier. 27.Give the classification of tuned amplifier: (i) Small signal tuned amplifier *Single tuned *Double tuned *Stagger tuned (ii) Large signal tuned amplifier. 28.List the applications of Isolation amplifier. • Floating pulse amplifier output voltage and current interface. • Instrumentation in high-noise environments. • Analogue front-end processing. • Medical instrumentation. 29.What are the advantages of switched capacitor filters? • Very high value of resistors can be easily simulated using small value capacitors, of the order of 10pF. • The switched capacitor filters require no external reactive components like inductors and capacitors. • Completely active filters can be easily obtained on a monolithic IC chip. • Good temperature stability, high accuracy and low cost. 30.Define drop-out voltage of a fixed voltage regulator. It is the minimum voltage that must exist between input and output terminals. It is defined as the ratio of the r.m.s input ripple voltage to the r.m.s output ripple voltage. It is expressed in decibels (dB). 31.Define video amplifier. A video amplifier has to amplify signals over a wideband of frequencies, say upto 20MHz. It is a RC coupled amplifier with bandwidth from d.c. to high frequency upto few megahertz.
VVCET – Dept. of ECE
Linear Integrated Circuits
Possible Part B Questions:Unit I 1. Fabrication process of Monolithic ICs 2. Realization of discrete circuits in monolithic ICs 3. DC analysis of differential amplifier 4. Differential amplifier with constant current source 5. Differential amplifier active load 6. Wilson current source circuit and widlar current source circuit 7. Band gap voltage reference circuit 8. Internal Stages of Op-amp 9. Methods to improve slew rate 10. AC & DC characteristics of Op-amp 11. Frequency response and stability of Op-amp 12. Internal and External frequency compensation techniques Unit II 1. Need and analysis of Instrumentation amplifier 2. Integrator and differentiator 3. Logarithmic and anti-logarithmic amplifier 4. Schmitt trigger and its applications 5. Precision rectifier and its applications 6. Analysis of low Butterworth filters 7. I to V and V to I converters and applications 8. Clipper and clamper circuits Unit III 1. Gilbert multiplier cell 2. Four quadrant multiplier 3. Analog multiplier using emitter coupled transistor 4. Operation of PLL 5. Operation of VCO 6. Closed loop analysis of PLL 7. Applications of PLL Unit IV 1. Weighted resistor type D/A converter 2. R-2R ladder type D/A converter – Voltage mode and current mode 3. Flash type A/D converter 4. Successive approximation type A/D converter 5. Dual Slope type A/D converter 6. Single slope type A/D converter 7. Sample and Hold circuits for A/D converter Unit V 1. Wien Bridge and RC phase oscillator using IC741 2. Triangular and saw tooth wave generator 3. Working of ICL 8038 function generator 4. Monosatble multivibrator using IC555 5. Astable multivibrator using IC555 6. Working of IC 723 general purpose regulator 7. Short notes on audio amplifier and its applications 8. Short notes on video amplifier 9. Short notes on Isolation amplifier 10. Short notes on Opto-couplers and fiber optic ICs Problems:- (Bakshi book) UNIT I Page no: 2-7, 2-14, 2-22, 3-26, 3-33, 3-34, 3-78 UNIT II Page no: 4-14, 4-23, 4-30, 4-122, 4-159, 5-18, 5-23 UNIT III Page no: 7-37, 7-42 UNIT IV Page no: 8-13, 8-14, 8-15, 8-27, 8-49 UNIT V Page no: 9-8, 9-46, 10-26, 10-38
VVCET – Dept. of ECE
Linear Integrated Circuits
List of ICs to study in our syllabus:LM741 General Purpose Op-amp AD533, AD534 Multiplier ICs NE566 VCO IC NE565 PLL IC LF398 Sample & Hold IC ICL8038 Function Generator IC NE555 Timer IC IC723 Voltage regulator IC78xx Three terminal fixed voltage regulator LM340 series Three terminal voltage regulators LM 317, 337, etc., Three terminal adjustable voltage regulators LM 320 series negative voltage regulators µA 78S40 Switching regulator MF10 Dual Switched capacitor filter LM 380 Audio power amplifier LM 384 Audio power amplifier IC 810 Audio power amplifier TC 9400, 9401, 9402 V to F and F to V converter MC 1550, CA 3040 Video amplifier MCT2E Opto-coupler ISO100 Isolation Amplifier Ideal Vs Practical Characteristics of Op-Amp:S.No 1 2 3 4 5 6 7 8 9 10
Parameter Open loop Voltage gain Output impedance Input impedance Input offset current Input offset voltage Bandwidth CMRR Slew rate Input Bias current Power supply rejection ratio
Symbol AOL Zout Zin Iios Vios BW ρ S Ib PSRR
Ideal ∞ 0 ∞ 0 0 ∞ ∞ ∞ 0 0
Typical for IC 741 2 x 105 75 Ω 2MΩ 20nA 2mV 1 MHz 90 dB 0.5 V/µsec 80nA 30 µV/V
VVCET – Dept. of ECE
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