Linear Integrated Circuits - Ec2254 29454n

EC2254 - Linear Integrated Circuits

LINEAR INTEGRATED CIRCUITS QUESTION BANK

Prepared By, V.MUTHULAKSHMI AP/ECE

VM/AP – Dept. of ECE


PART-A 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.  Miniaturization 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.  Metallization.  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 coating & 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 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 vapour 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 at which 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. VM/AP – Dept. of ECE


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. 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. Iios = |I b1-Ib2| 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. Sensitivity = dIo /dVo 29. What are the limitations in a temperature compensated zener-reference source? A power supply voltage of atleast 7 to 10V 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? VM/AP – Dept. of ECE


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-amp, 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. 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. Slew rate = dVo/dt 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 power-supply rejection ratio (PSRR). 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). PSRR = ΔVios/ ΔVCC |VEE = Constant PSRR = ΔVios/ ΔVEE |VCC = Constant 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. 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. VM/AP – Dept. of ECE


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. 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 op-amp 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 VM/AP – Dept. of ECE


 

high gain stability with low temperature co-efficient low dc offset and 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 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 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 VM/AP – Dept. of ECE


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. 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 i.e, 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. 32. Differentiate Schmitt trigger and comparator. S.No Comparator Schmitt trigger is not used that is Op-amp is used in is used that is Op-amp is 1. open loop mode used in closed loop mode False triggering due to noise voltages 2. False triggering due to noise voltages is possible. is not possible. A single reference voltage exists which acts as Two different threshold voltages 3. triggering voltage.i.e. Vref or -Vref exists as VUT and VLT 4.

The hysteresis exists with a width H=VUT - VLT

The hysteresis does not exists.

UNIT – 3: ANALOG MULTIPLIER AND PLL 1. 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. 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 VM/AP – Dept. of ECE


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 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. 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. 13. Give the expression for the VCO free running frequency. fo = 0.25 / RT CT 14. 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. 15. 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. 16. Mention some typical applications of PLL:  Frequency multiplication/division  Frequency translation  AM detection  FM demodulation  FSK demodulation. 17. What are the two types of analog multiplier Ics?  IC AD 533  IC AD 534 VM/AP – Dept. of ECE


18. 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. 19. List the features of ICAD533.  Its operation is very simple.  Only 4 external adjustments are necessary  Maximum 4 quadrant error is below 0.5% 20. 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. 21. List the features of ICAD534.  Adjustable scale factor  Low noise  Excellent long time stability 22. List the few applications of ICAD534.  Multiplier  Divider  High quality signal processing 23. 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. 24. 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. 25. 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 VM/AP – Dept. of ECE


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 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 VM/AP – Dept. of ECE


T---clock period Tc---conversion time n----number of bits 11. What is monotonic DAC? A monotonic DAC is one whose analog output increases for an increase in digital input. 12. 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. Resolution = ViFS / 2n-1 13. 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. 14. 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. 15. 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. 16. 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. 17. 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. 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 VM/AP – Dept. of ECE


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. 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 VM/AP – Dept. of ECE


 

Two comparator Discharge transistor.

6. Give the classification of voltage regulators:  Series / Linear regulators



Switching regulators.

7. 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. 8. 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. 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 continuous 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 continuously. 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. 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? VM/AP – Dept. of ECE


 

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 photo-sensing 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. 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. 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



PART – B SHORT HINTS UNIT I IC FABRICATION AND CIRCUIT CONFIGURATION FOR LINEAR ICs



Unit I- IC Fabrication and Circuit configurations for Linear ICs 1.

MANUFACTURING PROCESS OF MONOLITHIC ICS. (16M)  Silicon wafer preparation:





Epitaxial growth: Epitaxial growth is the formation of layer of Si crystal with n-type doping as an extension of the existing p-type Si substrate. The process is carried in a reactor at 1000 C where finished wafers the inserted. Si is obtained by breaking SiCl4 in presence of H2 : SiCl4 + 2 H2 --> Si + 4 HCl

Oxidation: Characteristics of SiO2 layer : • Acts as diffusion mask permitting selective diffusions into Si wafer • Used for surface ivation i.e. protecting junction from moisture and other atmospheric contaminants • Used for insulating the metal interconnections from Si





The silicon wafers are kept in quartz boat and inserted into a quartz tube. the tube is heated to 10001200 C such that temperature is uniform along the length of tube. Nitrogen, dry oxygen, steam is ed over the slices to grow the oxide layer . Si +O2  SiO2  Photolithography Photolithography or Optical lithography, is a process used in micro fabrication to selectively remove parts of a thin film or the bulk of a substrate. It uses light to transfer a geometric pattern from a photo mask to a light-sensitive chemical photo resist, or simply "resist," on the substrate. A series of chemical treatments then engraves the exposure pattern into the material underneath the photo resist.



Diffusion: The process of introducing impurities into selected regions of a silicon wafer is called diffusion. The rate at which 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.

DIFFUSION



Ion implantation: It is the process by which the ions of a particular impurity or dopant material are accelerated by an electric field to a very high velocity and physically implant or lodge the dopant within the semiconductor material.





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.

VACUUM DEPOSITION



Circuit probing: The performance of each IIC fabricated on the wafer is checked electrically by placing probes on the bonding pads of the ICs. Faulty chips are identified and discarded after scribing and separating the individual chips from the wafer.  Scribing and separating into chips: The wafer in which hundreds of ICs are fabricated, is broken into individual chips by scribing with a diamond-tipped tool.  Mounting and packaging: Top hat, Flat package and dual-in line package ,



Encapsulation To protect it against mechanical and chemical damage while in use. It was done by placing a cap over the circuit and sealing it in a inert atmosphere. 2. CONSTRUCTION OF MONOLITHIC TRANSISTORS.  Epitaxial Growth  Oxidation  Photolithography  Isolation Diffusion  Base Diffusion VM/AP – Dept. of ECE


  

Emitter diffusion mask Aluminum Metallization

3. DISCUSS THE DIFFERENT WAYS TO FABRICATE DIODES.  The emitter-base diode, with the collector short circuited to the base  The emitter-base diode, with the collector open  The collector-base diode, with the emitter open-circuited

(8m)

4. WITH NEAT SKETCHES DESCRIBE THE VARIOUS TYPES OF INTEGRATED RESISTORS (6m)  Diffused resistor: If the resistor is formed in one of the isolated regions of epitaxial layer during base or emitter diffusion, then it is called as diffused resistor.





Sheet resistor: Consider a sheet of material with length L, width W, t be the thickness and ρ be the uniform resistivity,

R = Rs(L/W) the ratio L/W is called aspect ratio. Epitaxial resistor: By using n-epitaxial collector layer, large value resistances than base and emitter diffusion can be achieved. Such resistors are called epitaxial resistor. VM/AP – Dept. of ECE


5. EXPLAIN IN DETAIL ABOUT REALIZATION OF MONOLITHIC ICS. (10m) Realization of monolithic ICs: The key element in the IC is transistor, along with transistors, diodes, resistors and capacitors are also integrated over a single silicon wafer which is called monolithic IC.



Preparation of wafer :

Epitaxial growth:



Oxidation:

Lithographic process:



Isolation diffusion:

Base diffusion:



Emitter diffusion:

Metallization:



6. DC & AC ANALYSIS OF DIFFERENTIAL AMPLIFIER. (16M) DC analysis : The transistors Q1 and Q2 are matched transistors and hence for such a matched pair we can assume: i) Both the transistors have the same characteristics. ii) RE1 = RE2 hence RE = RE1|| RE2. iii) RC1 = RC2 hence denoted as RC. iv) |VCC| = | VEE| and both are measured with respect to ground.

AC analysis :  Differential gain: Ad = Vo/Vs = -hfeRc/2(Rs+hie) (For unbalanced output) 

Common mode gain:

Ac = Vo/Vs = -hfeRc/(Rs+hie+2RE(1+hfe)) 

Differential input impedance:

Ad = Vo/Vs = hfeRc/2(Rs+hie) (Magnitude) CMRR: CMRR= (Rs+hie+2RE(1+hfe))/(Rs+hie)

Output impedance: Ro = Rc

Ri = 2(Rs+hie)

7. DIFFERENTIAL AMPLIFIER WITH CONSTANT CURRENT SOURCE.  Circuit diagram:

(10m)

IE3 = (VEE(R2/R1+R2)-VBE)/R3





Temperature compensation: IE3 = (2VD-VBE)/R3



IE3 = (VEE-1.4V)/IE3

Constant current bias using zener:

R1 = (VEE-VZ)/I

IE3 = (VZ-VBE)/R3

8. DRAW AND DERIVE THE EXPRESSION FOR CURRENT MIRROR AND IMPROVED CURRENT MIRROR CIRCUIT. (10m) Current mirror : The circuit in which the output current is forced to equal the input current is called as current mirror circuit.

I2 = (IC3+ IC3(2/β)

I2 = (VEE- VBE3)/R2

Improved current mirror circuit: I1 = (IB( β (1+β )+2)/(1+β)

I2 = (I1β (1+β ))/ (β(1+β)+2)



9. WILSON CURRENT SOURCE CIRCUIT AND WIDLAR CURRENT SOURCE CIRCUIT. Wilson current source circuit:

(16m)

IC2 = (Iref( 1-(2/( β2+2β+2)

Widlar current source circuit:

IC1/IC2 = e(VBE1-VBE2)/VT

REIC2 = VT ln( IC1/IC2 )

10. BAND GAP VOLTAGE REFERENCE CIRCUIT. (10m) The zener diodes and temperature compensated avalanche diodes have breakdown voltage in the range of 6v to 7v. Thus the supply voltages required are of the order of 10v or more. Hence it is no possible to use zener references circuits in lower supply voltage circuits, such cases use bandgap voltage reference circuits. VR3 = VT ln (IC1/IC2) IC2 = VT/R3 ln (IC1/IC2) Vref = VBE3 + (R2/R3) VT ln (IC1/IC2) Vref = VG0 + 3VT

11. METHODS TO IMPROVE SLEW RATE. (10m) 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. Slew rate = dVo/dt |max VM/AP – Dept. of ECE


C = gm1/2πft

S= 2π (I01(sat)/gm1)ft

12. COMPARE IDEAL AND PRACTICAL CHARACTERISTICS OF OPAMP. 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

13. AC & DC CHARACTERISTICS OF OP-AMP. DC characteristics of Op-amp:  Thermal drift  Effect on input offset voltage  Effect on input offset and bias currents

Ideal ∞ 0 ∞ 0 0 ∞ ∞ ∞ 0 0

(6m) Typical for IC 741 2 x 105 75 Ω 2MΩ 20nA 2mV 1 MHz 90 dB 0.5 V/µsec 80nA 30 µV/V (8m)

Thermal drift in input bias current = ΔIb/ ΔT Thermal drift in input bias current = ΔIios/ ΔT

AC characteristics of Op-amp: Frequency response of op-amp:

UGB = AOLfo UGB = Af ff fo = UGB/AOL

|AOL(f)|= AOL/(1+j(f/fo))



14. STABILITY OF OP-AMP.

x = Vo/ AOL(f) |AOL(f)β| = 1

(6m)

Vo/Vin = AOL(f)/(1+ AOL(f)β) |AOL(f)β| = 0o or 2nπ radians

AOL(f)β = -1

G.M = -20 log |AOL(f)β|ω = ωpc dB P.M = 180O + |AOL(f)β| ω = ωgc dB

15. INTERNAL AND EXTERNAL FREQUENCY COMPENSATION TECHNIQUES. External frequency compensation:  Dominant pole compensation  Pole-zero compensation  Feed-forward compensation Dominant pole compensation:

(10m)

A1 = 1+ j(f/fd) A’ = AOL/((1+ j(f/fd))(1+ j(f/f1))(1+ j(f/f2))(1+ j(f/f3)) Pole-zero compensation:

A1 = [1+ j(f/f1)] / [1+ j(f/f0)] A’ = AOL(1+ j(f/f1) / [(1+ j(f/f0))(1+ j(f/f1))(1+ j(f/f2)) (1+ j(f/f3)]



Feed-forward compensation: Vin

A1

A2

V0

H(jf) = j(f/fo) /[1+ j(f/fo)]

A = A1 A2 Internal compensation:  Miller effect compensation:

fd = 1 / (2πCMRi)



PART – B SHORT HINTS UNIT II APPLICATIONS OF OPERATIONAL AMPLIFIERS



Unit II- Applications of Op-amp 1. PHASE SHIFT CIRCUIT. (10m) A phase shifter circuit is one in which all signals are transmitted from input to output without change in amplitude but the circuit introduces a phase shift s signal transmits from input to output.

V0(s)/Vin(s) = (1-sCR)/(1+sCR) V0(jω)/Vin(jω) = (1- jωCR)/(1+ jωCR) Magnitude : |Vo |= |Vi| Phase angle: φ =-tan-1(ωCR/1)-tan-1(ωCR/1)

2. DIFFERENCE AMPLIFIER. (8m) The subtraction of two input voltages is possible with the help of op-amp circuit, called subtractor or difference amplifier.

V0 = aV2-bV1

Case1:

V01 = -(Rf/R1)V1

Case2:

V01 = (Rf/R1)(V2-V1)



3. NEED AND ANALYSIS OF INSTRUMENTATION AMPLIFIER. (16m) Definition: The special amplifier which is used for low level amplification with high CMRR, high input impedance to avoid loading, low power consumption and some other features is called an Instrumentation amplifier. It is also called as data amplifier. A = (V0/V1-V2) Instrumentation amplifier with three OP-AMP:

V0 = R2/R1(1+ (2Rf/RG))(V2-V1)

Instrumentation amplifier with two OP-AMP:

AV = (1+(Rf/R1)+(2R2/R3))

4. INTEGRATOR AND DIFFERENTIATOR. (8m) Integrator: In an integrator circuit, the output voltage is the integration of the input voltage. The integrator circuit can be obtained without using active devices like op-amp, transistor, etc..In such a case an integrator is called ive integrator. While an integrator using an active devices like op-amp is called active integrator.

Vo = -(1/R1Cf)∫ Vin dt + Vo(0)

Differentiator: The circuit which produces the differentiation of the input voltage at its output is called differentiator. The differentiator circuit which does not use any active device is called an ive differentiator. While the differentiator using an active device like op-amp is called an active differentiator.

Vo = -R1Cf (dVin/dt )



5. LOGARITHMIC AND ANTI-LOGARITHMIC AMPLIFIER. (8m) Logarithmic amplifier: The fundamental log amplifier is formed by placing a diode or a transistor in the negative path of the op-amp. Using diode Using transistor

Vo = -ηVT ln (Vin/Vref)

Vo = -VT ln (Vin/Vref)

Anti-Logarithmic amplifier: The log amplifier can easily be turned around to provide the antilog or exponential function which is called antilog amplifier. Using diode Using transistor

Vo = -Vref(e(Vin/ηVT)

Vo = -Vref(e(Vin/ηVT)

6. Schmitt trigger and its applications. (10m) The wrong indication of zero crossing due to zero crossing of noise voltage rather than zero crossing of input wanted signal. Such unwanted noise causes the output to jump between high and low states. The comparator circuit used to avoid suac unwanted triggering is called regenerative comparator or Schmitt trigger.



Inverting Schmitt trigger:

+Vref = (Vo/(R1+R2))R2 = (+Vsat/(R1+R2))R2 -Vref = (Vo/(R1+R2))R2 = (-Vsat/(R1+R2))R2 H = (2 VsatR2 / (R1+R2))

Non- Inverting Schmitt trigger:

VUT = +Vsat (R2 /R1) VLT = -Vsat/(R2 / R1) H = 2 Vsat/(R2 / R1)

Applications:  Schmitt trigger for eliminating comparator chatter  Schmitt trigger in ON/OFF controller 7. PRECISION RECTIFIER AND ITS APPLICATIONS (10m) The circuit that keeps V0 equal to Vi for Vi > 0 ,this can be achieved using op-amp along with the diodes and these circuits is called Precision rectifier. These are used to precisely rectify voltages having amplitudes less than .7V. Hence these circuits are called small signal precision rectifier. Precision half wave rectifier: Non-inverting: Inverting:



Precision Positive Full wave rectifier: Case1: Vi>0 Vo = |Vi|

Precision negative Full wave rectifier: Case2: Vi<0 Vo = - |Vi|

8. Analysis Of Second Order Low Butterworth Filters. Circuit diagram: Analysis:

(10m)

Vo(s)/Vin(s) = A/(s2+2ξωn+ωn2)

|Vo/Vin| = AF/√(1+(f/fH)4)



9. I TO V AND V TO I CONVERTERS AND APPLICATIONS. V-I converter with floating load:

(6m) V-I converter with grounded load:

IL = Vi/R (or) IL α Vi Applications:  Low voltage d.c. voltmeter  Low voltage a.c. voltmeter  Diode tester and Match finder  Zener diode tester I-Vconverter: Applications:  Photodiode detector  PhotoFET detector Vo α Ii

10. CLIPPER AND CLAMPER CIRCUITS. (8m) Clipper circuit: The circuit that are used to clip off the unwanted portions of the input voltage above or below certain levels, so as to produce limited required output are called limiting circuit or clipper circuit.  The positive clipper circuit remove some positive part from the input to produce the output.  The negative clipper circuit remove some negative part from the input to produce the output. Clamper circuit: The circuit which are used to add a d.c.level as per the requirement, to the a.c output are called as clamper circuit or restorer circuit.  If the clamped signal is positive, the circuit are called positive clamper circuits.  If the clamped signal is negative, the circuit are called negative clamper circuits. Positive clipper circuit:

Negative Clipper Circuit:



Positive clamper circuit:

Negative Clamper Circuit:

11. VOLTAGE FOLLOWER AND ADDER. (4m) Voltage follower: A circuit in which the output voltage follows the input voltage is called voltage follower circuit. It is also called as source follower, isolation amplifier, buffer amplifier or unity gain amplifier. Vo = Vin



Advantages:  Very large input resistance of the order of MΩ.  Low output impedance , almost zero.  Large bandwidth  Output follows input exactly without a phase shift. ADDER: Inverting Summer:

Vo = -(V1 + V2)

Non-Inverting Summer:

Vo = (V1 + V2)

Average circuit: Vo = (V1 + V2)/2



PART – B SHORT HINTS UNIT III

ANALOG MULTIPLIER AND PLL



Unit III- Analog multiplier and PLL 1. GILBERT MULTIPLIER CELL. Basic Gilbert cell

Vo =(RLV1)/VT[I5 – I6]

(16m) Variable transconductance multiplier

Vo = KV1V2 = 0.1 V1V2

2. ANALOG VOLTAGE MULTIPLIER CIRCUIT

Vo = K2V1 V2

3. APPLICATIONS OF MULTIPLIER. Voltage divider using multiplier:

(6m)

Vo = - (VN/KV2)

Squaring using multiplier: Vo = KV1V2 = K(V1)2



Square rooting circuit using multiplier:

Vo = √- (VN).(R1/KR2)

Frequency doubler using multiplier:

Vo = (KVm2)/2. cos2ωt

Phase angle detection using multiplier:

Vo = ((KV1mV2mcosѲ)/2)-( KV1mV2mcos(2ωt-Ѳ)/2)

RMS detector:

Rectifier using multiplier:



4. FOUR QUADRANT VARIABLE TRANSCONDUCTANCE MULTIPLIER.

(10m)

Linearized transconductance multiplier:

(I3-I4) = ((I1-I2)(I3+I4))/(I1+I2)

Differential V-I converter:

(I1-I2) = (2/Rx)(V1-V2)

Four quadrant multiplier:

Vo = K V1 V2

5. OPERATIONAL TRANSCONDUCTANCE AMPLIFIER. (16m) The operational transconductance amplifier is basically a voltage to current converter i.e. it is a voltage input, current output device. The constant of proportionality between input and output is nothing but the transconductance of the amplifier. Io = gm Vin VM/AP – Dept. of ECE


Symbolic Representation

Internal diagram

Transfer characteristics

Io = Ic tanh(V1 – V2/2VT) Av = gmRL = ICRL/2VT)

6. OPERATION OF VCO. (8m) 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. VCO circuit

Waveforms

Period of oscillation:

Kv = (1/(8Rc(VUT – VLT))



7. BASIC PLL OPERATION AND CLOSED LOOP ANALYSIS OF PLL Basic PLL operation:

(6m)

Closed loop analysis of PLL

ωo(t) = ωc + KoVf(t) Vf/ ωs = (KφF(s)A)/(s+KφKvF(s)A) 8. APPLICATIONS OF PLL. Frequency multiplier:

Vf/ ωs = (KφA)/(s+KφKvA) (6m)



AM detection:

Frequency translation:

Frequency synthesizer:

FM demodulator:

9. OPERATION OF 566 VCO AND DERIVE THE EXPRESSION FOR V-F CONVERSION FACTOR. (10m) 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. Features:  Wide supply voltage range(10-24V)  Very linear modulation characteristics  High temperature stability  Excellent power supply rejection  10 to 1 frequency range with fixed C1. IC 566 Connection diagram

V-F conversion factor:

Kv = (8fo/(+V))



PART – B SHORT HINTS UNIT IV

ANALOG TO DIGITAL & DIGITAL TO ANALOG CONVERTERS



Unit IV- Analog to Digital & Digital to Analog Converter 1. HIGH SPEED SAMPLE AND HOLD CIRCUITS, SAMPLE AND HOLD CIRCUITS & ANALOG SWITCHES. High speed Sample and hold circuits: (6m) 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.

Effect of changing input voltage

Input & output response

Principle Diagram Analog switches: 



Shunt switch: At VGS = 0

At VGS ≤ VGS(off)

At VGS = 0

At VGS ≤ VGS(off)

Series switch:



Types of Sample and hold circuits: Factors:  RC time constant  Maximum output current which can source or sunk by the op-amp.  Slew rate of the op-amp

2. TYPES OF D/A CONVERTER. (16m) Two techniques are:  Binary weighted resistor D/A converter  R/2R ladder D/A converter Binary weighted resistor D/A converter:

Vo = -VR(bo2-1+ b12-2+ b22-3+ ……+bn2-n



Inverted R/2R ladder/ Current mode R/2R ladder D/A converter:

Vo = -VR(bo2-1+ b12-2+ b22-3+ ……+bn2-n





R/2R ladder/ Voltage mode R/2R ladder D/A converter:

Current output: Voltage output:

 

Resolution = (1/2n)(VR/R) Resolution = (1/2n)(VR/R)Rf

Advantages: Easy to built accurately and Avoids slowdown effect Number of bits can be expanded by adding more sections of same R/2R values.

3. SINGLE SLOPE TYPE A/D CONVERTER.

(8m)

Limitations:  Its resolution is less.  Variation in ramp generator due to time, temperature or input voltage sensitivity also cause a lot of problems. 4. DUAL SLOPE A/D CONVERTER. (10m) Dual slope conversion is an indirect method for A/D conversion where an analog voltage and a reference voltage are converted into time periods by an integrator, and then measured by a counter.

Digital output = (counts/second)t2 Digital output = (counts/second)t1(Vi/VR)



5.

SUCCESSIVE APPROXIMATION A/D CONVERTER. (10m) Principle: 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. Block Diagram: Conversion Process:

Tc = T(n+1)

where Tc = conversion time T = clock period n = Number of bits

6. FLASH TYPE A/D CONVERTER. (8m) Principle: 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.

Number of comparators = 2n-1 Maximum frequency, fmax = (1/2πTc (2n)

7. SOURCES OF ERROR:  Linearity error: The error is defined as the amount by which the actual output differs from the ideal straight line output.



Linearity error

Offset error

 Offset error: The offset error is defined as the nonzero level of the output voltage when all inputs are zero.  Gain error: It is defined as the difference between the calculated gain of the current to voltage converter and the actual gain achieved.

8. A/D CONVERTER USING VOLTAGE TO TIME CONVERSION. (4m)

9. DELTA AND ADAPTIVE DELTA MODULATION.

(10m)

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. tive 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.



Advantages:  Simple technique  It represents each analog sample by one bit. Disadvantages:  Granular noise  Slope overload distortion Adap 10. OVER SAMPLING A/D CONVERTER. (10m) A/D converter where the input signal is sampled much faster than the Nyquist rate, is called an over sampling A/D converter. fN = 2fb The over sampling ratio is defined as the ratio between the sampling frequency and the Nyquist theorem. OSR = (fs/2fb)



PART – B SHORT HINTS UNIT V

WAVEFORM GENERATORS AND SPECIAL FUNCTION ICs



Unit V- Waveform generators & Special function ICs 1. WIEN BRIDGE AND RC PHASE OSCILLATOR USING IC741. RC phase oscillator- Circuit diagram:

α = (1/ωRC) |β| = 1/29

(10m)

f = (1/2πRC√6) |A| ≥ 29

Advantages:  The circuit is simple to design.  Can produce output over audio frequency range.  Produces sinusoidal output waveform.  It is a fixed frequency oscillator.  Disadvantages:  Frequency stability is poor.

Wien Bridge oscillator-Circuit diagram: Basic circuit

network

Simplified circuit

Z1 = (1+S1C1/SC1) f = 1/2πRC |β| = 1/3

Z2 = (R2/1+S2C2) f = 1/(2π√R1R2C1C2) |A| ≥ 3 |A β | ≥ 3



2. TRIANGULAR AND SAW TOOTH WAVE GENERATOR.

(8m)

i)Triangular waveform generator:

Amplitude and Frequency calculation: T = (4 R1R2C1/ R3) fo = (1/T) = (R3/4 R1R2C1) ii) Sawtooth waveform generator:

3. WORKING OF ICL 8038 FUNCTION GENERATOR. (10m) Definition: Function generators are designed to provide the basic waveforms such as square wave, triangular wave and sine wave. They are also called as waveform generators. Block diagram ICL 8038 function generator



Frequency of output waveform: fout = (3Vi/CRAVCC)(1-RB/2RA) fout = (1.5Vi/CRAVCC) %

d = (1-RB/2RA) x 100

4. ASTABLE MULTIVIBRATOR USING IC555.

(8m)

The astable multivibrator has both states as quasi-stable states. As this multivibrator does not require any external pulse for the transition, is called free running multivibrator. Block diagram

Waveforms

Duty cycle: %D = (W/T)x100%

T = 0.693( RA+2RB)C

%D =(( RA+RB)/(RA+2RB))x100

f = 1.44/( RA+2RB)C

5. MONOSTABLE MULTIVIBRATOR USING IC555.

(8m)

The monostable multivibrator has only one stable state. The other state is unstable referred as quasi stable state. The monostable multivibrator is also known as one-shot, single-shot, single-cycle, single-swing, single step multivibrator or a univibrator. Block diagram

Waveforms



Pulse width, W = 1.1RC Operation

6. TYPES OF VOLTAGE REGULATOR & IC 723 GENERAL PURPOSE REGULATOR. (16m) 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. Characteristics:  Load regulation  Source regulation  Output impedance  Ripple rejection  Load current  Temperature Types of Voltage regulator: Series Voltage regulator

Shunt Voltage regulator



IC 723 general purpose regulator: Block diagram

Applications:    

Basic low voltage regulator Low voltage high current regulator Basic positive high voltage regulator Negative voltage regulator

7. LM 317 VOLTAGE REGULATOR. Adjustable voltage regulator have the following advantages over fixed voltage regulators,  Improved line and load regulation by a factor of 10 or more  Greater load current can be drawn over the given operating temperature range.  Improved reliability for the power supply using these regulators. Schematic diagram

(8m)

Functional diagram

8. SWITCHING REGULATOR. (16M) SMPS: The pulse width modulation is the basic principle of the Switching regulator. The average value of repetitive pulse waveform is proportional to the area under the waveform.

Vo = δVin Types of Switching regulator: Step down Switching regulator(Buck):

Waveforms



Step up Switching regulator(Boost): Q1 is ON

Q1 is OFF

9. SWITCHED CAPACITOR FILTER. (10m) The switched capacitor filter use the on-chip capacitors of small values and MOS switches, to simulate high value resistors. The switches are controlled by the external clock, whose frequency can be easily controlled. Q = CVin Vin/Iave = 1/(CFclk) = R Iave = (V1 – V2)/R

R = 1/ CFclk R = Tclk/2C = 1/(CFclk)

Advantages:  Very high values of resistors can be easily simulated.  Complete active filters can be easily obtained.  Easily controllable.  Accuracy is very high.  Low cost  Good temperature stability  Small size Schematic diagram , Simulation diagram, Input and waveform, MF10 10. AUDIO POWER AMPLIFIER. Features:  The large amount of power to be delivered to the load.  Power efficiency  Impedance matching to the output device. Classification:

Class A amplifier

(16m)

Class B amplifier VM/AP – Dept. of ECE


Class AB amplifier

Class C amplifier

LM 380 Power audio amplifier: LM 380 is a popular power audio amplifier produced by National semiconductor. It is capable of delivering 2.5W minimum to 8Ω load. Hence it is much ideal for consumer applications. Internal circuit diagram of LM 380

Applications:  LM 380 Audio power amplifier  LM 380 with a variable gain  Intercom system using LM 380

  

LM 380 as High gain Audio amplifier Phono amplifier using LM 380 Siren/Alarm using LM 380

11. VIDEO AMPLIFIER. (10m) 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. Internal circuit diagram of CA 304 video amplifier



12. SHORT NOTES ON ISOLATION AMPLIFIER. (10m) An isolation amplifier is an amplifier that offers electrical isolation between its input and output terminals.  CMRR defines the relationship between a change in the applied common-mode voltage(VCM) and the change in IOS required to maintain the amplifier’s output at zero. CMRR (I – mode) = Δ IOS /Δ VCM in nA/V CMRR (V – mode) = (Δ IOS /Δ VCM)RIN = Δ VERR CM /Δ VCM in V/V



IMRR defines the relationship between a change in the applied isolation-mode voltage(VIM) and the change in IOS required to maintain the amplifier’s output at zero. IMRR (I – mode) = Δ IOS /Δ VIM in pA/V IMRR (V – mode) = (Δ IOS /Δ VIM)RIN = Δ VERR IM /Δ VCM in V/V

13. SHORT NOTES ON OPTO-COUPLERS AND FIBER OPTIC ICS. (8m) The combined package of a LED and a photodiode is called an optocoupler. It is also called an optoisolator or an optically coupled isolator. Types of optocoupler:  LED-Photodiode  LED-Photodarlington



Characteristics:  Current transfer ratio  Response time  VCE and IL Optocoupler

  

Isolation voltage Common mode rejection Bandwidth Types of optocoupler

14. FIBER OPTICS: Components of Fiber optics technology

Block diagram

15. V/F AND F/V CONVERTER. The frequency to voltage converter performs the reverse operation of the VFC. It accepts a wide range and variety of periodic waveforms and produces an analog single linearly proportional to the input frequency. Vo = Kf fin The TC 9400 is low cost VFC utilizing lower power CMOS technology. The converter accepts a variable anaput single and generates an output pulse train whose frequency is linearly proportional to the input voltage. Circuit diagram of VFC

Block diagram of TC 9400



Block diagram of TC 9400 using V/F & Block diagram of TC 9400 using F/V



BLUE PRINT & IMPORTANT QUESTIONS



UNIVERSITY QUESTION PAPERS



TWO MARKS QUESTION BANK



LESSON NOTES/STUDY MATERIAL



ASSIGNMENT QUESTIONS



SYLLABUS



EC 2254

LINEAR INTEGRATED CIRCUITS

3003

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 9 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 9 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 9 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 8 Analog and Digital Data Conversions, D/A converter – specifications - weighted resistor type, R-2R 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 Voltageto-Time Conversion - Over-sampling A/D Converters. UNIT - V WAVEFORM GENERATORS AND SPECIAL FUNCTION ICs 9 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. TOTAL : 45 PERIODS



TEXT BOOKS: 1. Sergio Franco, Design with operational amplifiers and anategrated circuits 3rdEdition, 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, 2ndEdition, 2001 2. Gray and Meyer, Analysis and Design of Anategrated Circuits, Wiley International2005. 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.



UNIT I – IC FABRICATION AND CIRCUIT CONFIGURATION FOR LINEAR ICs IMPORTANT QUESTIONS PART A 1. What is differential amplifier? What is the ideal value of its gain? 2. What is common mode gain of a differential amplifier? State its ideal value. 3. What is CMRR? State its ideal value. 4. List out various configurations of a differential amplifier. 5. What is voltage reference circuit? 6. List the performance parameters of a voltage reference circuit. 7. State the applications of bandgap reference circuit. 8. What is current mirror? What are its advantages. 9. What is an Op-amp? 10. Define offset voltage. 11. Define input bias current. 12. What are the limitations of monolithic ICs. 13. What is internally compensated op-amp? 14. What are the methods to improve the slew rate? 15. Define diffusion. 16. What is dielectric isolation? 17. What are the advantages of ion implantation technique? 18. What are the different types of lithography? What is optical lithography? 19. What is the advantage of widlar current source over constant current source? 20. Justify the reasons for using current sources in integrated circuits.

PART B 1. Manufacturing process of Monolithic IC’s 2. Differential Amplifiers 3. Current Mirror Circuit 4. Bandgap Voltage References 5. Current sources 6. DC & AC Characteristics of an OP-AMP. 7. Frequency Compensation



UNIT II – APPLICATIONS OF OPERATIONAL AMPLIFIERS IMPORTANT QUESTIONS PART A 1. What are the areas of application of non-linear op- amp circuits? 2. What is the need for an instrumentation amplifier? 3. What are the applications of V-I converter? 4. List the applications of Log amplifiers. 5. What is a comparator? 6. What is a Schmitt trigger? 7. What do you mean by monostable multivibrator? 8. What are the requirements for producing sustained oscillations in circuits? 9. What are the demerits of ive filters? 10. What are the advantages of active filters? 11. Define virtual ground property of Op-amp. 12. What is Voltage follower? 13. Define logarithmic and antilogarithmic amplifier. 14. Differentiate Schmitt trigger and comparator. 15. Define band filter. 16. What are the requirements for producing sustained oscillations in circuits? 17. What is a Schmitt trigger? 18. What do you mean by a precision diode? 19. What are the applications of V-I converter? 20. Mention some of the linear applications of op – amps

PART B 1. Adders 2. Subtractor 3. V-I & I-V Converters 4. Instrumentation amplifier 5. Integrator & Differentiator 6. Log & Antilog amplifiers 7. Schimitt Trigger 8. Precision Rectifier 9. Second Order LPF



UNIT III – ANALOG MULTIPLIER AND PLL IMPORTANT QUESTIONS PART A 1. Define VCO. 2. List the features of 566 VCO. 3. Mention some areas where PLL is widely used: 4. Define capture range of PLL 5. What is a switch type phase detector? 6. What is a voltage controlled oscillator? 7. Discuss the effect of having large capture range. 8. What is a compander IC? Give some examples. 9. What are the merits of companding? 10. List the applications of OTA 11. What is analog multiplier? 12. Differentiate digital and analog PLLs. 13. Define FSK modulation. 14. Define free running mode. 15. Mention some typical applications of PLL 16. Give the expression for the VCO free running frequency. 17. On what parameters does the free running frequency of VCO depend on? 18. List the features of 566 VCO. 19. What is ICAD 533? 20. List the features of ICAD533. 21. What is ICAD 534?

PART B 1. Applications of Multiplier 2. Variable transconductance techniques. 3. OTA 4. Voltage Controlled Oscillator. 5. Applications of PLL



UNIT IV – ANALOG TO DIGITAL & DIGITAL TO ANALOG CONVERTERS IMPORTANT QUESTIONS PART A 1. What is Adaptive delta modulation? 2. What is meant by delta modulation? 3. Define sample period and hold period 4. What is a sample and hold circuit? Where it is used? 5. What is monotonic DAC? 6. What is meant by linearity? 7. What is settling time? 8. Explain in brief stability of a converter: 9. Define accuracy of converter 10. Define resolution of a data converter 11. Define conversion time. 12. State the advantages of dual slope ADC: 13. What is the main drawback of a dual-slop ADC? 14. Where are the successive approximation type ADC’s used? 15. Explain in brief the principle of operation of successive Approximation ADC. 16. What is integrating type converter? 17. List out the direct type ADCs 18. List the broad classification of ADCs. 19. List out some integrating type converters. 20. What are the main advantages of integrating type ADCs?

PART B 1. High speed sample & Hold circuits 2. D/A Converters 3. A/D Converters 4. A/D converter using V to time Conversion



UNIT V – WAVEFORM GENERATORS AND SPECIAL FUNCTION ICs IMPORTANT QUESTIONS PART A 1. Define drop-out voltage of a fixed voltage regulator. 2. What are the advantages of switched capacitor filters? 3. List the applications of Isolation amplifier 4. Give the classification of tuned amplifier: 5. What is the need for a tuned amplifier? 6. What are the features of isolation amplifier? 7. Mention the advantages of opto-couplers: 8. What is the advantage of switching regulators? 9. What is an opto-coupler IC? Give examples. 10. Give the drawbacks of linear regulators: 11. What is the purpose of having input and output capacitors in three terminal IC regulators? 12. Define load regulation 13. Define line regulation. 14. Give some examples of monolithic IC voltage regulators: 15. What is a switching regulator? 16. List the features of 555 Timer? 17. List the applications of 555 timer in monostable mode of operation: 18. Mention some applications of 555 timer 19. List the basic blocks of IC 555 timer

PART B 1. Phase shift oscillators 2. Astable Multivibrator using opamp 3. Triangular Waveform generator 4. General Purpose IC723 regulator 5. Astable & Monostable Multivibrator using IC555 6. Switched Capacitor filter. 7. Frequency Volatage Converter 8. Opto coupler & Isolation Amplifier 9. Video Amplifier




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