112 + Interview Questions in Field-Effect Transistors in Electronic Devices & Circuits Page 1 InterviewSolution

1.	What are unijunction transistors used for?(a) Amplifying a circuit(b) Circuit breaker(c) Splitting device(d) On-Off switching deviceThe question was asked in an interview.The query is from The Unijunction Transistors topic in section Field-Effect Transistors of Electronic Devices & Circuits
Answer» The CORRECT option is (d) On-Off switching device To ELABORATE: Unlike bipolar transistors or FIELD EFFECT transistors these unijunction transistors cannot be used to amplify a circuit. The unijunction transistors are used as an on-off switching transistor. They have UNIDIRECTIONAL conductivity.

Discussion

2.	What will happen if values of Rs increase?(a) Vgs Increases(b) Vgs Decreases(c) Vgs Remains the same(d) Vgs=0The question was asked in a job interview.Asked question is from Biasing the FET in portion Field-Effect Transistors of Electronic Devices & Circuits
Answer» The correct answer is (B) Vgs Decreases Best explanation: Increasing VALUES of RS RESULT in lower quiescent values of ID and more NEGATIVE values of Vgs.

Discussion

3.	For an n-channel FET, What is the direction of current flow?(a) Source to drain(b) Drain to source(c) Gate to source(d) Gate to drainThe question was asked in exam.This interesting question is from The Junction Field-Effect Transistor in chapter Field-Effect Transistors of Electronic Devices & Circuits
Answer» CORRECT OPTION is (b) Drain to source Easy EXPLANATION: When a voltage greater than pinch off is APPLIED, the current STARTS flowing from Drain to source.

Discussion

4.	What is the value of drain current when Vgs=pinch off voltage?(a) 0A(b) 1A(c) 2A(d) Cannot be determinedThe question was asked during a job interview.This key question is from The Junction Field-Effect Transistor in chapter Field-Effect Transistors of Electronic Devices & Circuits
Answer» The correct ANSWER is (a) 0A The explanation: ID = IDSS (1-Vgs/VP)^2 IfVgs = Vp,then ID = IDSS (1-1)=0.

Discussion

5.	For a fixed bias circuit the drain current was 1mA, what is the value of source current?(a) 0mA(b) 1mA(c) 2mA(d) 3mAThe question was posed to me by my college professor while I was bunking the class.My query is from Biasing the FET topic in section Field-Effect Transistors of Electronic Devices & Circuits
Answer» The correct choice is (c) 2mA For explanation: We know that for an FET same current FLOWS through the GATE and source terminal, Hence source current=1mA.

Discussion

6.	While choosing the operating conditions, the Vgs value was set lesser toVt. What will the output if the FET is made to work as Source Follower?(a) 0(b) Same as the input(c) Same as input but phase reversed(d) Cannot be determinedI got this question in homework.Enquiry is from The Common Drain Amplifier in section Field-Effect Transistors of Electronic Devices & Circuits
Answer» CORRECT choice is (a) 0 The best EXPLANATION: If FET is needed to work as an amplifier, then the bias POINT must lie on Saturation, but in the above CASE the FET is operating in cut-off resulting in off condition. Hence OUTPUT will be 0.

Discussion

7.	Which of the following is the other name for Common Drain Amplifier?(a) Source Follower(b) Current Booster(c) Voltage booster(d) Voltage limiterI have been asked this question by my school principal while I was bunking the class.This key question is from The Common Drain Amplifier in section Field-Effect Transistors of Electronic Devices & Circuits
Answer» Correct CHOICE is (a) Source Follower To elaborate: The voltage gain for a Common Drain Amplifier, Av=1, hence the output at the source terminal FOLLOWS the input PROVIDED to the GATE terminal. Hence we call a Common Drain Amplifier as Source follower as the name itself says it the source terminal follows the input signal.

Discussion

8.	For a FET having IDSS=2mA Vgs=2V and Vp=-1V, What is the value of source current?(a) 9mA(b) 18mA(c) 3mA(d) 1mAI got this question in class test.My doubt stems from The Pinch off Voltage Vp in section Field-Effect Transistors of Electronic Devices & Circuits
Answer» Right CHOICE is (b) 18mA The BEST EXPLANATION: ID=IDSS (1-Vgs/Vp)^2 ID=IS=2×(1+2)(1+2)=3^2×2=18mA IS=18mA.

Discussion

9.	Which of the following effects can be caused by decrease in temperature?(a) Increase in MOSFET current(b) Increase in BJT current(c) Decrease in MOSFET current(d) Decrease in BJT currentThis question was addressed to me at a job interview.The question is from The Insulated-Gate FET(MOSFET) topic in portion Field-Effect Transistors of Electronic Devices & Circuits
Answer» CORRECT option is (c) Decrease in MOSFET current The explanation: MOSFET has positive temperature COEFFICIENT and drain resistance INCREASE with decrease in temperature .HENCE current decreases with decrease in temperature.

Discussion

10.	At room temperature, what is the possible value for the mobility of electrons in the inversion layer of a silicon n-channel MOSFET?(a) 450 cm^2/v-s(b) 1350 cm^2/v-s(c) 1800 cm^2/v-s(d) 3600cm^2/v-sI have been asked this question in final exam.This intriguing question comes from The Insulated-Gate FET(MOSFET) topic in chapter Field-Effect Transistors of Electronic Devices & Circuits
Answer» CORRECT answer is (B) 1350 cm^2/v-s Easy explanation: The mobility of electron in s-type Si semiconductor is 1350 cm^2/v-s. In INVERSION LAYER mobility of electron is 1350 cm^2/v-s.

Discussion

11.	Necessary condition to create a channel in n-channel enhancement MOSFET is ____________(a) Vgs > Vt(b) Vgs < Vt(c) Vgs < 2Vt(d) 2Vgs > VtI had been asked this question by my college professor while I was bunking the class.The above asked question is from The Insulated-Gate FET(MOSFET) in portion Field-Effect Transistors of Electronic Devices & Circuits
Answer» The CORRECT option is (a) VGS > Vt For explanation I would say: When gate to source VOLTAGE exceeds the threshold voltage, the source and substrate and drain and substrate forms a forward bias resulting in the formation of depletion region which acts as a channel.

Discussion

12.	Which of the following is true about MOSFET?(a) There is no direction between channel and gate terminal(b) There exists a channel and gate short connection(c) Channel is not present and cannot be created(d) They have low input impedanceThe question was asked by my school teacher while I was bunking the class.This intriguing question comes from The Insulated-Gate FET(MOSFET) in portion Field-Effect Transistors of Electronic Devices & Circuits
Answer» Right answer is (a) There is no direction between channel and gate TERMINAL The explanation: ACCORDING to the physical structure of MOSFET, there is a Silicon dioxide layer between channel and gate terminal. Since Silicon dioxide acts as a RESISTOR with infinite RESISTANCE, there is no connection between the channel and gate terminal of MOSFET.

Discussion

13.	What is the relation between the drain current and source current once the voltage crosses pinch off?(a) ID = IS(b) ID = IS + 1.5(c) ID = 1/IS(d) IS – 2ID = 0This question was addressed to me during an interview for a job.My question is from The Pinch off Voltage Vp in portion Field-Effect Transistors of Electronic Devices & Circuits
Answer» Right answer is (a) ID = IS Explanation: For a FET, once the voltage exceeds the pinch off voltage, the electrons will start flowing from source to drain or VICE VERSA, since no current flows through the gate terminal, the current transfer TAKES place only between the drain and source. Hence ID = IS.

Discussion

14.	In an n-channel E-MOSFET, the current becomes constant in saturation region. Which of the following condition depicts this?(a) VDS = 2Vgs-Vt(b) VDS > Vgs-Vt(c) VDS ≤ Vgs-Vt(d) VDS = VgsThis question was posed to me in examination.Question is taken from The Insulated-Gate FET(MOSFET) in portion Field-Effect Transistors of Electronic Devices & Circuits
Answer» Correct option is (b) VDS > Vgs-Vt To explain I would say: The n-channel E-MOSFET operates in the saturation region when VDS > Vgs-Vt, since we will be fixing the gate to source voltage and threshold is a system constant, WHATEVER may be the VALUE of VDS which is greater than Vgs-Vt, the CURRENT remains the same.

Discussion

15.	What is pinch off voltage?(a) The minimum voltage required to turn on the FET(b) The maximum voltage a FET can withstand(c) Current amplification factor/voltage gain(d) The value of voltage at which the current gets pinched to zeroI have been asked this question in final exam.Asked question is from The Pinch off Voltage Vp topic in portion Field-Effect Transistors of Electronic Devices & Circuits
Answer» The CORRECT answer is (d) The value of voltage at which the current gets pinched to zero To explain I WOULD say: Once the voltage DIFFERENCE between the gate and source goes near to the pinch off voltage, the channel will GET pinched off resulting in off state of the FET, which MAKES no conventional current flow.

Discussion

16.	Comparing the size of BJT and FET, choose the correct statement?(a) BJT is larger than the FET(b) BJT is smaller than the FET(c) Both are of same size(d) Depends on applicationI have been asked this question during an online exam.This interesting question is from The Junction Field-Effect Transistor topic in portion Field-Effect Transistors of Electronic Devices & Circuits
Answer» The correct option is (a) BJT is larger than the FET Explanation: BJT usually are built with a THICKNESS of up to 1cm whereas the FET uses a fabrication TECHNIQUE which MAKES its size in mm.

Discussion

17.	At higher frequency, the capacitance of an amplifier circuit is mainly because of which capacitance?(a) Coupling capacitors(b) Stray capacitance(c) Resistors(d) InductorsThe question was posed to me in an interview for job.I want to ask this question from The Junction Field-Effect Transistor topic in portion Field-Effect Transistors of Electronic Devices & Circuits
Answer» The correct answer is (b) STRAY capacitance To explain: During HIGH frequency, the stray capacitance is the only SOURCE of capacitance in an amplifier CIRCUIT, the stray capacitance and JUNCTION capacitance.

Discussion

18.	Which of the following is the equation for stray capacitance frequency?(a) FH = 1/27R(b) FH = 1/R(c) FH = 54/27R(d) FH = 11/27RI had been asked this question by my college professor while I was bunking the class.The doubt is from The Junction Field-Effect Transistor topic in portion Field-Effect Transistors of Electronic Devices & Circuits
Answer» CORRECT CHOICE is (a) FH = 1/27R Explanation: During high frequency the capacitance is due to combination of TRANSMISSION capacitance and JUNCTION capacitance. The equation is given by FH = 1/27R.

Discussion

19.	How many terminals are there in a unijunction transistor?(a) 1(b) 2(c) 3(d) 4The question was asked during an online interview.My doubt stems from The Unijunction Transistors topic in division Field-Effect Transistors of Electronic Devices & Circuits
Answer» The correct choice is (c) 3 To explain: A unijunction transistor consists of THREE terminals. It is a semiconductor device that DISPLAYS negative RESISTANCE and switching characteristics. It is used as a relaxation OSCILLATOR in phase CONTROL applications.

Discussion

20.	Which of the following equations gives the relation between ID and Vgs?(a) ID=IDSS (1-Vgs/Vp)^2(b) ID=IDSS (1-Vgs/Vp)^1(c) ID=IDSS (1-Vgs/Vp)^3(d) ID=IDSS (1-Vgs/Vp)^4This question was addressed to me in exam.My question is taken from Biasing the FET in chapter Field-Effect Transistors of Electronic Devices & Circuits
Answer» Right option is (a) ID=IDSS (1-Vgs/Vp)^2 For explanation: The above equation called as Shockley’s equation depicts the relation between ID and Vgs. When Vgs BECOMES equal toVp, the CURRENT will become ZERO, which clearly SATISFIES the physical nature of FET.

Discussion

21.	Which of the following is true about the effects of rdin Drain amplifier?(a) rd Increases output impedance(b) rd Decreases output impedance(c) Output impedance remains the same(d) rd Increases input impedanceThis question was posed to me by my college professor while I was bunking the class.The doubt is from The Common Drain Amplifier topic in chapter Field-Effect Transistors of Electronic Devices & Circuits
Answer» The correct answer is (B) RD Decreases output impedance For explanation I WOULD SAY: Typically ZO=c\|\|1/gm But with rd, ZO=RS\|\|1/gm\|\|rd, Hence output impedance will decrease.

Discussion

22.	An amplifier is designed using fixed bias configuration, what is its output impedance (source Resistor is bypassed)?(a) RD+rd(b) RG(c) RD \|\| rd(d) 0The question was posed to me in an online quiz.Asked question is from The Common Source Amplifier topic in portion Field-Effect Transistors of Electronic Devices & Circuits
Answer» Right option is (c) RD \|\| rd Easy explanation: By using ac equivalent of FET, gm Vgs is MADE 0. On observing the circuit from OUTPUT side, ZO=RD \|\| rd, where RDis the drain resistance. In general, rd>>RD, ZO=RD.

Discussion

23.	Which of the following is true about Common Drain amplifier?(a) It has low input impedance(b) It has high output impedance(c) Infinite gain(d) Output will be same as inputThe question was posed to me in a national level competition.The above asked question is from The Common Drain Amplifier in portion Field-Effect Transistors of Electronic Devices & Circuits
Answer» CORRECT option is (d) Output will be same as input Easiest EXPLANATION: The voltage gain for a COMMON Drain AMPLIFIER, Av=1, hence the output at the source terminal follows the input provided to the gate terminal.

Discussion

24.	Given yfs = 3.6mS and yos = 0.02mS, determine r0?(a) 100Kohm(b) 50Mohm(c) 50Kohm(d) 20KohmI have been asked this question in an interview.This question is from The FET Small-Signal Model in section Field-Effect Transistors of Electronic Devices & Circuits
Answer» CORRECT OPTION is (c) 50Kohm Best EXPLANATION: r0=1/yos It is independent ofyfs. => r0=1/20mS r0=50Kohm.

Discussion

25.	How does a FET behave when the v-I characteristics are to the left of pinch off for an n channel FET?(a) Voltage controlled resistor(b) Amplifier(c) Switch(d) DiodeI have been asked this question by my school teacher while I was bunking the class.The query is from The Pinch off Voltage Vp topic in portion Field-Effect Transistors of Electronic Devices & Circuits
Answer» Correct ANSWER is (a) Voltage controlled RESISTOR Explanation: When the voltage Vgs is less than pinch off voltage, there will be no current flow, resulting in Ohmic region, on controlling the Vgs and VDs VALUES, the FET ACTS as Voltage controlled resistor.

Discussion

26.	What is trans-conductance?(a) Ratio of change in drain current to change in collector current(b) Ratio of change in drain current to change in gate to source voltage(c) Ratio of change in collector current to change in drain current(d) Ratio of change in collector current to change in gate to source voltageI have been asked this question in homework.My doubt stems from The FET Small-Signal Model topic in division Field-Effect Transistors of Electronic Devices & Circuits
Answer» Right option is (b) Ratio of change in drain CURRENT to change in gate to source voltage Easy EXPLANATION: The change in drain current which is resulted due to change in gate to source voltage in a FET is MEASURED by trans-conductance. This is TERMED as trans because it provides relationship between input and output quantity.

Discussion

27.	For a fixed bias circuit the drain current was 1mA, VDD=12V, determine drain resistance required if VDS=10V?(a) 1KΩ(b) 1.5KΩ(c) 2KΩ(d) 4KΩI have been asked this question in class test.I'm obligated to ask this question of Biasing the FET in chapter Field-Effect Transistors of Electronic Devices & Circuits
Answer» RIGHT CHOICE is (C) 2KΩ Explanation: VDS=VDD-ID RD =>10=12-RD×1mA =>RD=2/1mA=2 KΩ.

Discussion

28.	What is the intrinsic stand-off ratio(η) of a unijunction transistor when RB1 = 10kΩ and RBB = 15kΩ?(a) 0.67(b) 0.55(c) 0.80(d) 0.44This question was addressed to me during an interview for a job.This interesting question is from The Unijunction Transistors in portion Field-Effect Transistors of Electronic Devices & Circuits
Answer» The CORRECT option is (a) 0.67 To elaborate: The intrinsic stand-off ratio(η) is equal to the ratio RB1 / RBB. Standard VALUES of η RANGE from 0.5 to 0.8. Given RB1 = 10kΩ and RBB = 15kΩ: η = RB1 / RBB = 10 / 15 = 0.67

Discussion

29.	A sinusoidal signal has 1.5V at t=2S, If this signal is given to Common drain amplifier, what will be its output at t=2S?(a) 7.5V(b) -7.5V(c) 0(d) 1.5VI have been asked this question in class test.My question is based upon The Common Drain Amplifier topic in division Field-Effect Transistors of Electronic Devices & Circuits
Answer» CORRECT ANSWER is (d) 1.5V The EXPLANATION: INPUT at t=2S is 1.5V, \|Av\|=1 =>output=1×1.5V=1.5V.

Discussion

30.	What will happen if a metal is used instead of Silicon dioxide in the fabrication of MOSFET?(a) Device burns(b) No changes in the behaviour of MOSFET(c) Input impedance increases(d) Current cannot be generated in MOSFETThis question was addressed to me in final exam.The origin of the question is The Insulated-Gate FET(MOSFET) in section Field-Effect Transistors of Electronic Devices & Circuits
Answer» The correct answer is (a) Device burns Explanation: If a METAL is used instead of Silicon DIOXIDE, once the biasing condition is achieved, as the drain to source VOLTAGE current starts floating to gate terminal RESULTING in burning of the device.

Discussion

31.	For a FET, graph is drawn by taking voltage VGSin X axis and drain current in Y axis, if the value of X changes from 10 to 20 results in change in value of Y axis from 2 to 3. What is the value of trans conductance?(a) 1(b) 2(c) 0.1(d) 0.01I have been asked this question during an online exam.My doubt stems from The FET Small-Signal Model in portion Field-Effect Transistors of Electronic Devices & Circuits
Answer» CORRECT OPTION is (C) 0.1 For EXPLANATION: Trans-conductance= change in DRAIN current/ change in gate to source voltage trans conductance=3-2/20-10=1/10 trans conductance=0.1.

Discussion

32.	Find the current through gate if the FET was given with gate to source voltage =10V and drain to source voltage =20V, the pinch off voltage was -2V and ID=2mA.(a) 10mA(b) 20mA(c) 0mA(d) 2mAThe question was asked in a national level competition.This interesting question is from The Pinch off Voltage Vp in division Field-Effect Transistors of Electronic Devices & Circuits
Answer» Correct ANSWER is (c) 0mA Best explanation: We know that for a FET, the gate terminal is heavily doped with an insulator, resulting in INFINITE RESISTANCE. Hence no current flows through the gate terminal. It has no relationship with the other current parameters. It is constant for all FETS.

Discussion

33.	A p-channelGe JFET has max-half channel width 5µm and channel conductivity of 2/Ωcm, if Er = 2000cm^2/Vsec, What is the value of pinch off voltage?(a) 8.21V(b) 82.1V(c) 88.21V(d) 5.2VI had been asked this question in a national level competition.The question is from The Pinch off Voltage Vp in division Field-Effect Transistors of Electronic Devices & Circuits
Answer» RIGHT ANSWER is (C) 88.21V Best EXPLANATION: Vp=qNA a^2/2E = (5×10^-4) (5×10^-4)×2/(2×16×8.854×2000×10^-14) = 88.21V.

Discussion

34.	A common source amplifier has _______(a) no source resistance(b) no drain resistance(c) no gate resistance(d) low input impedanceI had been asked this question during an interview.The question is from A Generalized FET Amplifier topic in portion Field-Effect Transistors of Electronic Devices & Circuits
Answer» Correct option is (a) no source resistance To explain I would say: In a COMMON source amplifier the source resistance is connected to the ground(i.e. is GROUNDED) because of which its source resistance is kept ZERO.

Discussion

35.	A Common drain amplifier is designed using fixed bias configuration, what is its input impedance?(a) RD + rd(b) RG(c) RD \|\| rd(d) 0I have been asked this question in class test.Question is from The Common Drain Amplifier topic in portion Field-Effect Transistors of Electronic Devices & Circuits
Answer» The correct answer is (B) RG To explain: From the ac small signal model, the input impedance of FET is OPEN circuit. Gate resistance RGIS in parallel with open circuit RESULTING in Zin=∞\|\|RG=RG.

Discussion

36.	A sinusoidal signal has 1.5V at t=2S, If this signal is given to Common source amplifier with \|Av\|=5V, what will be its output at t=2S?(a) 7.5V(b) -7.5V(c) 0(d) 15VI got this question in final exam.This question is from The Common Source Amplifier topic in division Field-Effect Transistors of Electronic Devices & Circuits
Answer» The correct OPTION is (B) -7.5V Explanation: Input at t=2S is 1.5V, \|Av\|=5V=> output=5×1.5V=7.5V, But amplifier PRODUCES 180 DEGREE phase-shift => output=-7.5V.

Discussion

37.	What is the reason for connecting a capacitor in parallel with Rs?(a) It blocks the noise(b) For ac signal it acts a short circuit resulting in grounding source terminal(c) It blocks the noise & for ac signal it acts a short circuit resulting in grounding source terminal(d) To increase impedanceI had been asked this question in quiz.This question is from The Common Source Amplifier topic in section Field-Effect Transistors of Electronic Devices & Circuits
Answer» Right ANSWER is (C) It blocks the noise & for ac signal it acts a short circuit resulting in GROUNDING source terminal To explain: The capacitor connected acrossSource blocks all the DC noise signals, when AC input is applied, at high frequency the capacitive reactance will be almost zero resulting in short circuit making the source to be DIRECTLY connected to ground.

Discussion

38.	The threshold voltage of an n-channel MOSFET can be controlled by which of the following parameter?(a) Increasing the channel dopant concentration(b) Reducing the channel dopant concentration(c) Reducing the gate-oxide thickness(d) Reducing the channelI had been asked this question during a job interview.This interesting question is from The Insulated-Gate FET(MOSFET) in division Field-Effect Transistors of Electronic Devices & Circuits
Answer» The correct answer is (B) Reducing the CHANNEL dopant CONCENTRATION For EXPLANATION: The THRESHOLD voltage of n-channelMOSFET can be increased by reducing the channel dopant concentration or by increasing the oxide thickness.

Discussion

39.	For what value of Vgs, the drain current will be 1/4th of its maximum current?(a) 0(b) 1(c) Vp(d) Vp/2I got this question in examination.I'd like to ask this question from The Pinch off Voltage Vp in section Field-Effect Transistors of Electronic Devices & Circuits
Answer» RIGHT choice is (d) Vp/2 The BEST I can explain: ID=IDSS (1-Vgs/Vp)^2 WhenID=IDSS/4 => (1-Vgs/Vp)^2 = 1/4 =>(1-Vgs/Vp)^2=1/2 =>Vgs=Vp/2.

Discussion

40.	FET amplifier does not obey the law of conservation of energy.(a) True(b) FalseThe question was asked in an international level competition.My doubt is from The Junction Field-Effect Transistor in section Field-Effect Transistors of Electronic Devices & Circuits
Answer» The correct ANSWER is (b) False To ELABORATE: Amplifier OBEYS the law of conservation of energy.

Discussion

41.	Which of the following is an expression for gm0?(a) gm0 = IDSS/Vp(b) gm0 = 2IDSS/\|Vp\|(c) gm0 = IDSS/5Vp(d) gm0 = IDSS/2VpI had been asked this question in an interview.I'd like to ask this question from The FET Small-Signal Model in section Field-Effect Transistors of Electronic Devices & Circuits
Answer» Right answer is (B) gm0 = 2IDSS/\|Vp\| The explanation is: gm0is the value of gm when VGS=0, we have SEEN thattrans conductance is the ratio of drain current to changein GATE to source voltage, but this is an EXCEPTIONAL CASE, here the transistor will be working in cut off region.

Discussion

42.	What will be the gain value of FET if gmo=0?(a) 0(b) 1(c) 2(d) InfiniteI got this question in an interview for job.This interesting question is from The Common Drain Amplifier in division Field-Effect Transistors of Electronic Devices & Circuits
Answer» The correct answer is (a) 0 Easy explanation: Av=gm RS/(1+gm RS) but gmis having LINEAR relationship with gmo. Since gmo=0, VOLTAGE gain will be ZERO resulting in 0 Output.

Discussion

43.	If gain is need to be stabilized, which of the following element is used for a Common source amplifier?(a) Capacitive(b) Inductive(c) Resistive(d) LC tank circuitThis question was posed to me during an interview for a job.The above asked question is from The Common Source Amplifier in division Field-Effect Transistors of Electronic Devices & Circuits
Answer» Correct answer is (C) Resistive Best EXPLANATION: The negative feedback is GIVEN through a RESISTOR which stabilizes the gain. Hence a resistor is connected across source terminal. Any TEMPERATURE changes will not result in fluctuation of the output because of the negative feedback.

Discussion

44.	Which of the following statement is true about FET common source amplifier compared to BJT amplifier?(a) It has High input impedance(b) It has low input impedance(c) No input Voltage is needed(d) Input Voltage is neededThe question was posed to me by my college director while I was bunking the class.My enquiry is from The Common Source Amplifier topic in portion Field-Effect Transistors of Electronic Devices & Circuits
Answer» Correct answer is (a) It has HIGH input impedance Explanation: FET DUE to its physical nature has very high input impedance; hence the voltage drop in input side will be very LESS making the entire signal to pass through the input port.

Discussion

45.	In a MOSFET operating in a saturation region, the channel length modulation effect causes(a) An increase in gate-source capacitance(b) Decrease in Trans conductance(c) Decrease in the unity gain cut off(d) Decrease in the output impedanceI have been asked this question in an interview for job.This is a very interesting question from The Insulated-Gate FET(MOSFET) in portion Field-Effect Transistors of Electronic Devices & Circuits
Answer» The CORRECT answer is (d) DECREASE in the output impedance The EXPLANATION is: Under channel LENGTH modulation, 1/rds=dIds/dVds=dIDsat=1/ro Hence it decreases from ∞ to 1/ro.

Discussion

46.	What is the value of current when the gate to source voltage is less than the pinch off voltage?(a) 1A(b) 5A(c) 100A(d) 0This question was posed to me during an online interview.I want to ask this question from The Junction Field-Effect Transistor topic in portion Field-Effect Transistors of Electronic Devices & Circuits
Answer» Right choice is (d) 0 Easiest explanation: When the GATE to SOURCE VOLTAGE is LESS than pinch off, both of the junctions will be reverse biased and hence no current flows.

Discussion

47.	What are the terminals of a unijunction transistor?(a) Collector, Base and Emitter(b) Emitter, Base 1 and Base 2(c) Gate, Drain and Source(d) Gate, Drain, Body and SourceThe question was asked in semester exam.I would like to ask this question from The Unijunction Transistors topic in division Field-Effect Transistors of Electronic Devices & Circuits
Answer» The correct option is (b) Emitter, Base 1 and Base 2 Best explanation: The unijunction TRANSISTOR consists of a single solid piece of N-type channel with its two outer connections marked as Base 2 and Base 1. The third connection is the Emitter and it is LOCATED along the channel. The emitter LIES CLOSER to base 2 as compared to base 1.

Discussion

48.	Unijunction transistors have unidirectional conductivity and positive impedance characteristics.(a) True(b) FalseI have been asked this question in homework.My enquiry is from The Unijunction Transistors topic in section Field-Effect Transistors of Electronic Devices & Circuits
Answer» Correct answer is (B) False Explanation: Unijunction transistors have UNIDIRECTIONAL conductivity and NEGATIVE impedance characteristics. During circuit breakdown, they function more as a variable voltage divider. They are used in gate pulse, TIMING circuits and trigger GENERATION.

Discussion

49.	The drain of FET is analogous to BJT(a) collector(b) emitter(c) base(d) drainI got this question in unit test.Question is taken from A Generalized FET Amplifier topic in portion Field-Effect Transistors of Electronic Devices & Circuits
Answer» Right option is (a) COLLECTOR To explain: A common collector amplifier (also KNOWN as an emitter follower) is ONE of three basic single-stage bipolar junction transistor (BJT) amplifier, typically used as a voltage buffer. In this circuit the BASE terminal of the transistor serves as the input, the emitter is the output, and the collector is common to both. The analogous field-effect transistor circuit is the common drain amplifier and the analogous tube circuit is the cathode follower.

Discussion

50.	A common gate amplifier has _______(a) low input impedance(b) high input impedance(c) infinite input impedance(d) no impedanceI got this question in examination.I need to ask this question from A Generalized FET Amplifier in section Field-Effect Transistors of Electronic Devices & Circuits
Answer» The correct option is (a) low INPUT impedance To ELABORATE: Common GATE amplifier just like common base amplifier had a very large voltage gain but input impedance is very low. Also, it GIVES unity current gain. Hence, the POWER of the amplified signal will be less.

Discussion

Explore topic-wise InterviewSolutions in .

What are unijunction transistors used for?(a) Amplifying a circuit(b) Circuit breaker(c) Splitting device(d) On-Off switching deviceThe question was asked in an interview.The query is from The Unijunction Transistors topic in section Field-Effect Transistors of Electronic Devices & Circuits

What will happen if values of Rs increase?(a) Vgs Increases(b) Vgs Decreases(c) Vgs Remains the same(d) Vgs=0The question was asked in a job interview.Asked question is from Biasing the FET in portion Field-Effect Transistors of Electronic Devices & Circuits

What is the value of drain current when Vgs=pinch off voltage?(a) 0A(b) 1A(c) 2A(d) Cannot be determinedThe question was asked during a job interview.This key question is from The Junction Field-Effect Transistor in chapter Field-Effect Transistors of Electronic Devices & Circuits

For a FET having IDSS=2mA Vgs=2V and Vp=-1V, What is the value of source current?(a) 9mA(b) 18mA(c) 3mA(d) 1mAI got this question in class test.My doubt stems from The Pinch off Voltage Vp in section Field-Effect Transistors of Electronic Devices & Circuits

How many terminals are there in a unijunction transistor?(a) 1(b) 2(c) 3(d) 4The question was asked during an online interview.My doubt stems from The Unijunction Transistors topic in division Field-Effect Transistors of Electronic Devices & Circuits

Given yfs = 3.6mS and yos = 0.02mS, determine r0?(a) 100Kohm(b) 50Mohm(c) 50Kohm(d) 20KohmI have been asked this question in an interview.This question is from The FET Small-Signal Model in section Field-Effect Transistors of Electronic Devices & Circuits

A Common drain amplifier is designed using fixed bias configuration, what is its input impedance?(a) RD + rd(b) RG(c) RD || rd(d) 0I have been asked this question in class test.Question is from The Common Drain Amplifier topic in portion Field-Effect Transistors of Electronic Devices & Circuits

For what value of Vgs, the drain current will be 1/4th of its maximum current?(a) 0(b) 1(c) Vp(d) Vp/2I got this question in examination.I'd like to ask this question from The Pinch off Voltage Vp in section Field-Effect Transistors of Electronic Devices & Circuits

FET amplifier does not obey the law of conservation of energy.(a) True(b) FalseThe question was asked in an international level competition.My doubt is from The Junction Field-Effect Transistor in section Field-Effect Transistors of Electronic Devices & Circuits

Which of the following is an expression for gm0?(a) gm0 = IDSS/Vp(b) gm0 = 2IDSS/|Vp|(c) gm0 = IDSS/5Vp(d) gm0 = IDSS/2VpI had been asked this question in an interview.I'd like to ask this question from The FET Small-Signal Model in section Field-Effect Transistors of Electronic Devices & Circuits

What will be the gain value of FET if gmo=0?(a) 0(b) 1(c) 2(d) InfiniteI got this question in an interview for job.This interesting question is from The Common Drain Amplifier in division Field-Effect Transistors of Electronic Devices & Circuits

Unijunction transistors have unidirectional conductivity and positive impedance characteristics.(a) True(b) FalseI have been asked this question in homework.My enquiry is from The Unijunction Transistors topic in section Field-Effect Transistors of Electronic Devices & Circuits

The drain of FET is analogous to BJT(a) collector(b) emitter(c) base(d) drainI got this question in unit test.Question is taken from A Generalized FET Amplifier topic in portion Field-Effect Transistors of Electronic Devices & Circuits

A common gate amplifier has _______(a) low input impedance(b) high input impedance(c) infinite input impedance(d) no impedanceI got this question in examination.I need to ask this question from A Generalized FET Amplifier in section Field-Effect Transistors of Electronic Devices & Circuits