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EDC lab Viva Questions part1 Basics ~ ECE School
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EDC lab Viva Questions part-1 Basics 21:15
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1. What is the difference b/w Electronics and Electrical? Electronics is the science which deals with
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the currents in semiconductor materials, Vacuum
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tubes.Where electrical deals wwith the currents in
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conductors
2.What are types of materials? conductors (Energy gap is zero) semiconductors (Energy gap is narrower) (si 1.1ev,ge 0.7ev) Insulators (energy gap is widest). 3.What are the Semiconductor and conductors? Semiconductor which has 4 electrons in its valance band, and conductors has more than 4 electrons its valance band (best conductors: Ag,Al,Cu) 4. Difference b/w intrinsic and extrinsic Semiconductors? Ans: intrinsic semiconductors are pure semiconductors, Extrinsic are impure, i.e.by adding impurities (tri, pentavalent)Extrinsic semiconductors created(P,N Type). 5.What are the type in Extrinsic semiconductors and how the formed? P-Type and N-Type by adding trivalentimpurities (arsenic, antimony, phosphorus) P-Type semiconductors created.by adding pentavalent impurities (aluminum, boron) N-Type semiconductors created. 6.What is Doping? The processes of adding impurities. 7.How the PN Junction will be formed? In a piece of semiconductor material, if one half is doped by P type impurity and the other half is doped by N type impurity 8.What is Barrier Potential (cut in voltage)? The forward voltage at which the current through the junction starts increasing rapidly 9.What is Forward bias and Reverse bias? In diode’s anode(P) voltage is more than cathode(N) voltage its forward bias, if anode voltage is less than cathode voltage its reverse bias. 10.What is Diffusion and Drift currents? http://eceschool.blogspot.in/2016/10/electronicdevicesandcircuitslabvivaquestionspart1.html
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10/31/2016
EDC lab Viva Questions part1 Basics ~ ECE School
Drift current depends on the electric eld applied, if there is no electric eld there is no drift current. Diffusion current occurs even though there is not an electric eld applied to the semiconductor. 11.What is mean by 1n4007? 1n – single junction 400x-is indicates the voltage, current and power 4007 reverse voltage from 50v to 1000v, max forward current is 1A 12.What is the Diode current Equation? I=Io(e(V/nVT)-1), Io-Reverse saturation current,n=1,ge,2 si 13.De ne PIV(Peak inverse voltage)? It is the maximum reverse voltage that can be applied to the Diode. if the voltage across the junction exceeds PIV, under reverse bias condition, the junction gets damaged. 14.De ne Reverse saturation current? It is the current due to the diffusive ow of minority electrons from pside to N- side, and minority holes from N- side to P- side 15.How do we test a diode using a multimeter? Connect anode of dide to + terminal of multimeter and cathode to Negative terminal if voltage is 0.3 to 0.7 then diode is good. 16.Explain the capacitive effects in a junction. Diffusion capacitance occurs in Forward bias, Transition capacitance exist in Reverse Bias. 17.What is mean by Break down, difference b/w avalanche Break down and Zener Break down? Avalanche breakdown occurs in PN diode due to impact ionization of electron-hole pair, zener braek down occurs in Zener dioade due to electron hole pair break due to reverse bias voltage 18.What is the temperature effect on reverse saturation current and barrier voltage? Reverse saturation doubles for every 10 degrees increment in temperature Barrier voltage decreases by 2.5mv for every 1 degree increment in temperature 19.What is mean by static and dynamic resistances? Static resistance is the ratio of V,I at operating (Q) point, dynamic resistance is inverse to the slope of the forward bias characteristics curve at operating point. 20.What are the PN Diode, Zener diode applications? PN:recti er,switch,clipper,clapper Zener Diode:voltage regulator 21.Difference b/w PN, Zener Diode? Pn is lightly doped, Zener heavily doped 22.Why is a Zener diode generally not connected in forward bias? Zener gives the same response as pn diode in forward bias, so it uses in reverse bias only with Zener break down http://eceschool.blogspot.in/2016/10/electronicdevicesandcircuitslabvivaquestionspart1.html
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EDC lab Viva Questions part1 Basics ~ ECE School
23.What is the effect of Temperature on Zener diode? For Vz(Break down voltage) less than 6v Vz is inversely proportional to temperature,For Vz(Break down voltage) more than 6v Vz is directly proportional to temperature. 24. Why silicon is more preferred than germanium? For Si break Down voltage Is more than Ge, reverse saturation current Is less in Si, Si is cheap (raw material Is sand)
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10/31/2016
electronic devices and circuits lab viva questions part2 Rectifiers ~ ECE School
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Recti ers:
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1.What is the difference b/w AC and DC supply, what are the
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advantages of each? Ac supply is sinusoidal function of t, but Dc supply is constant for every time, dc can be storable but not Ac, Ac can transfer for a long distance but not Dc. 2.What is meant by regulation? Why is it required? It is a measure change in the magnitude between the sending and receiving end of a component. 3.How to convert AC to DC? Step down Transformer – Recti er – Filter -- Regulator 4.What are the requirements of Linear mode power supply? Should give minimum operable DC voltage at rated current, ripples should low, should have short circuit protection, over voltage protection, should independent of temparature changes 5.What is transformer and types? Transformer works based on Induction Principle, when Two coils are placed nearly then voltage transfer exist, Types: Step down, step up Transformer 6.What is recti er, lter, regulators? Recti er coverts AC to pulsating DC Filter coverts the pulsating DC to Fluctuating DC Regulator convers uctuating DC to exat DC 7.What are the various types in recti ers and which one is best and why?
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Half, Full wave , Bridge Recti er. Bridge recti er is best because PIV is less, ef ciency more, ripple factor less, TUF is more, peak facor less, transformer cost is less. 8.De ne ripple factor, ef ciency, transformer utilization factor, form factor, peak factors? Ripple factor= RMS value of ac component/Average value Ef ciency= dc output power / ac input power TUF= dc power delivered to load/ac rating of transformer secondary http://eceschool.blogspot.in/2016/10/electronicdevicesandcircuitslabvivaquestionspart2Rectifiers.html
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electronic devices and circuits lab viva questions part2 Rectifiers ~ ECE School
Form factor=rms/ average Peak factor= peak value/ rms value 9.De ne average value, RMS value, what is the signi cance of each? Average is de ned as sum per count, i.e mean. Or area of one cycle per time period RMS is Root of Mean(average) of squares. If data contains Both +,_ signs then average value can not give perfect idea about it, then Rms value gives idea about data. 10.Compare all recti ers?
11.Explain the importance of ripple and regulation in the case of a recti er. Ripple factor gives the idea about uctuations in signal, if it is less means ripples are less for DC ripple factor is Zero. Regulation gives idea about the variation of DC output voltage as a function of DC load current % regulation =(VNL-VFL)/VFL X 100% [ideal power supply its 0] 12.Explain why only the inductor or the capacitor alone is not used as lters to a FWR circuit. In inductor lter Ripple factor is inversely proportional to load, In capacitor lter Ripple factor is proportional to load, so in LC lter ripple factor will be independent of load. 13.What are the different lters used in AC to DC converters? Which is best and why? L,C,LC(L-section), π-section, RC lters. Best one is L-section because ripple factor is independent of load 14.Compare different lters?
15.De ne line regulation and load regulation? Line reg= change in output voltage/ change in input voltage Load reg= (no load voltage- full load voltage)/ no load voltage 16.De ne knee current? It is the minimum amount of voltage which is required to operate Diode 17.De ne knee current? It is the minimum current through Zener diode in reverse bias http://eceschool.blogspot.in/2016/10/electronicdevicesandcircuitslabvivaquestionspart2Rectifiers.html
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electronic devices and circuits lab viva questions part3 Bipolar Junction Transistor ~ ECE School
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BJT: 1.What is a transistor? A junction transistor is simply a sandwich of one
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type of semiconductor material between two layers of the other type. A
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transistor is a three terminal current sensing device. It can be looked upon
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as two pn junction placed back to back. The three terminals are named as emitter base & collector. 2.What is BJT, explain about its terminals, what are types, and which type is better, why? Bipolar junction Transistor in this corrent ows due to two polarities(electrons, holes), NPN or PNP type ,NPN is best because mobility of electrons is more than mobility of holes so electron current is more. 3.What are the different con gurations of transistor? a) Common Emitter (CE) b) Common Base (CB) c) Common collector (CC) 4.What is Common Base con guration? base is common between input and output circuits. emitter-base terminal input signal is applied and in collector-base terminal output is taken from it. 5.What are the characteristics of CB? since it has a low input resistance and a high output resistance, current gain of less than 1. The input and output signals in the common-base circuit are in phase 6.What is transistor and why it is called like that? Because it transfers the input signal from low resistance to high resistance 7.De ne α, β, γ, what is the relation between them? These are current gains in CB,CE,CC con gurations respectively, ; αγ=
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8.Compare CE,CC,CB con gurations?
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electronic devices and circuits lab viva questions part3 Bipolar Junction Transistor ~ ECE School
9.De ne cut-off, active and saturation regions? Cut off- both emitter Je, collector Jc junctions in Reverse bias Active – Je forward, Jc Reverse bias Saturation – Je,Jc in forward bias 10.What do you understand by input and output characteristics? ? 11.Explain the physical structure of a BJT? One N type material is sandwiched between two P type materials or One P type material is sandwiched between two N type materials , widths (C>E>B), doping concentration(E>C>B) 12.Explain Early Effect? The variation in base width of BJTdue to variation in the applied bacecollector voltage 13.Why does the emitter current increase with increase in reverse bias at the collector junction? Due to breakdown in collector junction 14.What is meant by collector reverse saturation current? Minority carriers
ow throw collector junction when it is connected in
reverse bias 15.Write the collector current expression for BJT in CB con guration? Cutoff region Ic=0 Active regionIc= βIb Saturation Ic<βIb 16.Give the values of VCE Sat for the transistor BC107. Vce sat=0.2v 17.Explain the performance of the transistor as an electronic switch? When transistor is in cut off it works as off switch, when transistor is in saturation it works as on switch 18.Is the BJT Transistor a current controlled device or a voltage-controlled device? Current controlled current device 19.Draw the symbolic representations of NPN and PNP transistors.
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electronic devices and circuits lab viva questions part3 Bipolar Junction Transistor ~ ECE School
20.Sketch the characteristics of a BJT in Common-Emitter Con guration.
21.Why is it called Common-Emitter con guration? Emitter terminal is common to input and out put 22.What is a “load-line”? What is its signi cance? Differentiate between a.c. load line and d.c. load line. Load line speci es the operating point, Dc load line is the line based on the relation between output voltage and currents when input is zero, Ac load line is the line which pocess through the Q point with slope of (-1/Rac, Rac= Rc//Rl) 23.What is meant by Q- point? It speci es the correct biasing at which gives required ampli cation 24.What is Biasing and why it is needed for transistor? The process of giving proper supply voltage and resistances for obtaining desired operating point 25.What are the methods of transistor biasing, which type is best and why? Fixed bias, Emitter bias, Collector to base bias, Collector- emitter bias, self bias(voltage divider bias), in these all self bias is best because it is more stable for a greater range of input signal 26.What is thermal Runaway? It is a situation where an increase in temperature changes the conditions in a way that causes a further increase in temperature. 27.Thermistor temperature co ef cient is? It may be + or – based on the material used. 28.De ne two port networks, types, which one is best for bjt and why? Z, Y, h, g, ABCD parameters, best one is hybrid parameters bczthethese gives all parameters about ampli er like input, output impedance, voltage and current gains. 29.What are the typical h-parameter values for a transistor?
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electronic devices and circuits lab viva questions part3 Bipolar Junction Transistor ~ ECE School
30.Draw the H parameter equivalent circuit?
31.Compare CB,CE,CC ampli ers, and what are the applications?
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Electronic Devices and circuits lab viva questions part4FET ~ ECE School
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Electronic Devices and circuits lab viva questions part4-FET 21:21
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FET 1.What are the comparisons and differences between a BJT and a JFET?
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BJT current controlled current device, Fet voltage controlled
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current device, in BJT current produced by holes and electrons, but in FET current produced due to any one only, 2.What is meant by a unipolar device? Why is a JFET known as a Unipolar Device? In which device current produced due to one polarity (electron or hole), in jFET current produced due to one only(N channel JFET- electrons, pchannel JFET- holes). 3.Draw the symbols of JFET, MOSFET?
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EDC lab Viva Questions part-1 Basics Home / Labs/Viva Questions/ Basics 1. What is the difference b/w Electronics and Electrical? Electronics is the science which deal... Gate/IES books Suggested Gate Books : GATE solved previous 29 years question papers with solutions by made easy GATE 2017 Guide by GK Publications ... Suggested Books For ECE students In this page you can buy the books from online. choose your subject: Tags: Suggeste... basic elctronics projects using 555 timer 555 Timer based projects op amp based projects Know more about 555 Timer 555 timer based projects: Mosquito,insec... Powered by Blogger.
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4.What are the typical applications of a JFET? Buffer, RF ampli er, cascade ampli er, variable resistor in op amps, mixer circuit, memory cell 5.What are the characteristic parameters of a FET? What are the relations between them?
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Electronic Devices and circuits lab viva questions part4FET ~ ECE School
Trans conductance gm=dId/dVgs Drain resistance Rd=dVds/dId Ampli cation factor µ=-dVds/dVgs µ=RdXgm 6.What are n-channel and p-channel JFETs? How are they different from each other? In N channel jfet , the channel made by Ntype material so current exist from Drain to source due to Electrons (ajority carriers) only. In P channel jfet , the channel made by P type material so current exist from Drain to source due to holes (ajority carriers) only 7.Give the names/numbers of a few commercially available JFET devices. 2N3954A- low noise low drift monolithic dual, N channel jfet BF245A, J111,J112: N channel jfet 8.What are the various possible con gurations in which a JFET can be connected? What are the typical applications of each? Common Drain: Buffer Common Sourse: Ampli er Common Gate: Ampli er (high frequency) 9.Explain pinch off voltage and region? Pinch off voltage is the drain to source voltage after which drain current becomes almost constant 10.Explain the regions in Transfer characteristics, output characteristics of JFET?
11.What is the drain current and Trans conductance equation in JFET? Id= Idss(1-(Vgs/Vp))2; gm=gmo(1-( Vgs/Vp)) 12.What is a MOSFET? What are the possible types in a MOSFET? Metal oxide semiconductor FET Types are N channel, P channel – Enhancement and Depletion Type Mosfets. 13.Which transistor parameters vary with temperature? Reverse saturation current, current gains, trans conductance 14.What is meant by ‘load line’? http://eceschool.blogspot.in/2016/10/electronicdevicesandcircuitslabvivaquestionspart4FET.html
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Electronic Devices and circuits lab viva questions part4FET ~ ECE School
Load line indicates the output side voltage, current relation based on input voltage or current. Inter section point of AC,DC load lines indicates Operating point(Q point) 15.What is meant by the “operating point” of a transistor? Operating point speci es output voltage and currents at required operating region. 16.Why is a capacitor used to shunt the emitter resistor of self-biased transistor? To get more stability we need to establish current series (-ve) for DC input but for Ac input that is not required so.. 17.Why is the self-bias circuit preferred over other possible biasing circuits? More stable with respect to Tempareture, β, 18.De ne Stability factor and explain its signi cance. Stability factor represents changes with in the output current due to changes in Temperature, transistor (β), leackage current, base emitter voltage 19.What is the advantage of a FET biasing circuit above BJT biasing? FET is a voltage controlled current device so no need of extra circuitry 10.What is the need for the capacitor CS? To get more stability we need to establish current series (-ve) for DC input but for Ac input that is not required so.. 11.Why are the coupling capacitors required? To lter the Dc term from the Input signal , Collector output in ampli ers. 12.What is meant by thermal stabilization? Maintain a constant operating point when temperature varies 13.Explain why reversal of phase occurs in a BJT CE Ampli er.\ As Base voltage increases, base current increases, then collector current increases so voltage drop across Rc increases so out put voltage decreses. 14.What happens if an ampli er is biased at cutoff or at saturation? In cutoff region Ic is 0, in saturation region Vce is almost Zero. 15.What is the signi cance of the bandwidth of an ampli er? Bandwidth speci es the input signal frequency range that can be applied to ampli er to get maximum gain. 16.What is meant by Gain-Bandwidth Product? What is its signi cance?
The name itself expressing it is the product of gain of a device and its bandwidth. For any system (circuit) gain bandwidth product is constant, if gain increases bandwidth decreases vice versa. 17.What are the advantages of using a FET instead of a BJT? FET has high input impedance, lower noise, low to medium gain, 19.Can we interchange the source and drain terminals in a FET circuit? Can we do the same with the emitter and collector terminals of a BJT circuit? We can interchange drain and source but we cannot change emitter and collector
because
emitter
and
collectors
dimensions
and
doping
concentration is different 20.What is a MOSFET? How is it different from a JFET? What are its typical applications? Metal oxide semiconductor can be operated in both depletion and enhancement modes, but Junction eld effect Transistor can be operated in depletion mode only. http://eceschool.blogspot.in/2016/10/electronicdevicesandcircuitslabvivaquestionspart4FET.html
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