Field Effect Transistor – FET MCQ

21. For a JFET, if the gate voltage VGS is made more negative, then

  1. the channel conductivity increases
  2. depletion region increases
  3. channel conductivity decreases
  4. channel current increases
Answer. c

22. The main drawbacks of a JFET is its

  1. high input impedance
  2. low input impedance
  3. higher noise
  4. lower gain
Answer. d

23. A field effect transistor (FET)

  1. has three pn junction
  2. uses a forward-biased junction
  3. depends on the variation of a reverse voltage for its operation
  4. depends on the variation of magnetic field for its operation
Answer. c

24. The operation of a JFET involves

  1. a flow of minority carriers
  2. a flow of majority carriers
  3. recombination
  4. negative resistance
Answer. b

25. What is the range of a FET’s input impedance?

  1. 10 Ω to 1 kΩ
  2. 1 kΩ to 10 kΩ
  3. 50 kΩ to 100 kΩ
  4. 1 MΩ to 100 MΩ
Answer. d

26. A FET is a better chopper than a BJT because it has

  1. lower offset voltage
  2. higher series ON resistance
  3. lower input current
  4. higher input impedance
Answer. a

27. In a N-channel JFET, drain current is maximum when gate voltage VGS is

  1. equal to +VDD
  2. more than to + VDD
  3. equal to ‘0’ volts
  4. all the above
Answer. c

28. Which of the following is a common feature of FET?

  1. They have high input impedance
  2. These are voltage-controlled devices
  3. They have isolated input and output
  4. all of these
Answer. d

29. FET belongs to which of the following type of device?

  1. current-controlled device
  2. magnetic device
  3. power controlled device
  4. voltage-controlled device
Answer. d

30. The control parameter of JFET is

  1. gate current
  2. drain voltage
  3. gate voltage
  4. source voltage
Answer. c

31. The transit time of the current carriers through the channel of a FET decides its ___________ characteristics.

  1. switching
  2. on/off
  3. dynamic
  4. load
Answer. a

32. As compared to FET, BJT has _________ input impedance and _________ output impedance.

  1. low, low
  2. low, high
  3. high, high
  4. high, low
Answer. a

33. The following statements refer to an n channel FET operated in the active region:

  1. the gate voltage VGS reverse biases the junction.
  2. The drain voltage VDD is negative with respect to the source.
  3. the current in the n channel is due to electrons.
  4. increasing the reverse bias VGS increases the cross section for conduction.

Which of these statements are correct?

  1. i and ii
  2. i and iii
  3. ii and iii
  4. iii and iv
Answer. b

34. Compared to the bipolar junction transistor, a JFET

  1. has a larger gain bandwidth produce
  2. is less noisy
  3. has less input resistance
  4. has current flow due to only majority carriers
  1. i, ii, iii and iv are correct
  2. i and ii are correct
  3. ii and iv are correct
  4. iii and iv are correct
Answer. c

35. Thermal runaway is not encountered in FETs because

  1. IDS has a zero temperature coefficient
  2. IDS has a negative temperature coefficient
  3. IDS has a positive temperature coefficient
  4. the mobility of the carriers increases with increase in temperature
Answer. b

36. A JFET is set up as a follower, with μ = 200, rd = 100 kΩ and source load resistor RL = 1 kΩ. The output resistance Ro is

  1. 1000 Ω
  2. 500 Ω
  3. 333 Ω
  4. 666 Ω
Answer. c

37. Consider following statements:

  1. BJT is a current controlled device with high input impedance and high gain bandwidth
  2. FET is a voltage controlled device with high input impedance and low gain bandwidth
  3. UJT is a negative resistance device and can be used as an oscillator
  4. BJT, FET and UJT can all be used for amplification.

Which of these statements are correct?

  1. i and ii
  2. ii and iii
  3. iii and iv
  4. i and iv
Answer. b