Electronics Device and Circuits – Field Effect Transistors MCQs

In this section of Electronic Devices and Circuits.It contain Field Effect Transistors MCQs (Multiple Choice Questions Answers).All the MCQs (Multiple Choice Question Answers) requires in depth reading of Electronic Devices and Circuits Subject as the hardness level of MCQs have been kept to advance level.These Sets of Questions are very helpful in Preparing for various Competitive Exams and University level Exams.

This Section covers below lists of topics :

1. Field Effect Transistors MCQs.
2. Junction Field Effect Transistor (JFET) MCQs
3. Metal oxide semiconductor field effect transistor – MOSFET MCQs

Practice it now to sharpen your concept.

PRACTICE IT NOW TO SHARPEN YOUR CONCEPT AND KNOWLEDGE

1. The transconductance increases when the drain current approaches

• 0
• ID(sat)
• IDSS
• IS

C. IDSS

2. A CS amplifier has a voltage gain of

• gmrd
• gmrs
• gmrs/(l + gmrs)
• gmrd/(l + gmrd)

A. gmrd

3. A source follower has a voltage gain of

• gmrd
• gmrs
• gmrs/(l + gmrs)
• gmrd/(l + gmrd)

C. gmrs/(l + gmrs)

4. When the input signal is large, a source follower has

• A voltage gain of less than one
• A small distortion
• A high input resistance
• All of these

D. All of these

5. The input signal used with a JFET analog switch should be

• Small
• Large
• A square wave
• Chopped

A. Small

6. A cascode amplifier has the advantage of

• Large voltage gain
• Low input capacitance
• Low input impedance
• Higher gm

B. Low input capacitance

7. VHF stands for frequencies from

• 300 kHz to 3 MHz
• 3 to 30 MHz
• 30 to 300 MHz
• 300 MHz to 3 GHz

C. 30 to 300 MHz

8. When a JFET is cut off, the depletion layers are

• Far apart
• Close together
• Touching
• Conducting

C. Touching

9. When the gate voltage becomes more negative in an N channel JFET, the channel between the depletion layers

• Shrinks
• Expand
• Conduct
• Stop conducting

A. Shrinks

10. If a JFET has IDSS = 10 mA and VP = 2 V, then RDS equals

• 200 ohm
• 400 ohm
• 1 kohm
• 5 kohm

A. 200 ohm

11. The easiest way to bias a JFET in the ohmic region is with

• Voltage-divider bias
• Self-bias
• Gate bias
• Source bias

A. Voltage-divider bias

12. Self-bias produces

• Positive feedback
• Negative feedback
• Forward feedback
• Reverse feedback

B. Negative feedback

13. To get a negative gate-source voltage in a self-biased JFET circuit, you must have a

• Voltage divider
• Source resistor
• Ground
• Negative gate supply voltage

B. Source resistor

14. Transconductance is measured in

• Ohms
• Amperes
• Volts
• Mhos or Siemens

D. Mhos or Siemens

15. Transconductance indicates how effectively the input voltage controls the

• Voltage gain
• Input resistance
• Supply voltage
• Output current

D. Output current

16. Which of the following devices revolutionized the computer industry?

• JFET
• D-MOSFET
• E-MOSFET
• Power FET

C. E-MOSFET

17. The voltage that turns on an EMOS device is the

• Gate-source cutoff voltage
• Pinch-off voltage
• Threshold voltage
• Knee voltage

C. Threshold voltage

18. Which of these may appear on the data sheet of an enhancement-mode MOSFET?

• VGS(th)
• ID(on)
• VGS(on)
• All of the above

D. All of the above

19. The VGS(on) of an n-channel E-MOSFET is

• Less than the threshold voltage
• Equal to the gate-source cutoff voltage
• Greater than VDS(on)
• Greater than VGS(th)

D. Greater than VGS(th)

20. An ordinary resistor is an example of

• A three-terminal device
• An active load
• A passive load
• A switching device

C. A passive load

21. An E-MOSFET with its gate connected to its drain is an example of

• A three-terminal device
• An active load
• A passive load
• A switching device

B. An active load

22. An E-MOSFET that operates at cutoff or in the ohmic region is an example of

• A current source
• An active load
• A passive load
• A switching device

D. A switching device

23. CMOS stands for

• Common MOS
• Active-load switching
• p-channel and n-channel devices
• Complementary MOS

D. Complementary MOS

24. VGS(on) is always

• Less than VGS(th)
• Equal to VDS(on)
• Greater than VGS(th)
• Negative

C. Greater than VGS(th)

25. With active-load switching, the upper E-MOSFET is a

• Two-terminal device
• Three-terminal device
• Switch
• Small resistance

A. Two-terminal device

26. A FET as a three terminal namely , source ,drain and

• Grid
• Substrate
• Ground
• Gate

D. Gate

27. from the output characteristics, FET is considered to be a solid state device equivalent to a

• Diode valve
• tetrode valve
• pantode valve
• none of these

C. pantode valve

28. A FET is essentially

• Current driven device
• Voltage driven device
• Power driven device
• None of these

B. Voltage driven device

29. a FET is a

• unipolar transistor
• Bipolar transistor
• Tripolar transistor
• None of these

A. unipolar transistor

30. The input impedance of a FET is of the order of

• 10^20 ohms
• Hundreds of mega ohms
• Hundred ohms
• a few ohms

B. Hundreds of mega ohms

31. A FET is characterized by

• Current gain
• Voltage gain
• Power gain
• None of these

B. Voltage gain

32. Before connecting a FET in the circuit

• Its source and drain terminals are interchangeable
• It source and drain terminals are not interchangeable
• Its drain terminal is marked
• None of these

A. Its source and drain terminals are interchangeable

33. The noise level in FET is

• More than BJT
• Negligibly small
• Slightly less than BJT
• None of these

B. Negligibly small

34. Input impedance of MOSFET is

• Less than that of FET but more than BJT
• More than that of FET and BJT
• More than that of FET but less than BJT
• Less than that of FET and BJT

B. More than that of FET and BJT

35. MOSFET uses the electric field of

• Gate capacitance to control the channel current
• Barrier potential of PN junction to control the channel current
• Both a and b
• None of these

A. Gate capacitance to control the channel current

36. FET is a:

• Unipolar device
• Bipolar device
• Tripolar device
• Not a device

A. Unipolar device

37. FET is a:

• Current-controlled device
• Voltage-controlled device
• Power-controlled device
• None of the above

B. Voltage-controlled device

38. The pinch-off voltage of JFET is 5.0 volts. Its cut-off voltage is:

• (5.0)^1/2 V
• 5.0 V
• 2.5 V
• (5.0)^3/2V

B. 5.0 V

39. An n-channel JFET has a pinch-off voltage of V_p = –5 V, V_DS (max) = 20 V, and g_m= 2 mA/V. The minimum ON resistance is achieved in the JFET for:

• VGS = –7 V and VDS = 0 V
• VGS = 0 V and VDS = 0 V
• VGS = 0V and VDS = 20 V
• VGS = –7 V and VDS = 20 V

B. VGS = 0 V and VDS = 0 V

40. The threshold voltage of an n-channel MOSFET can be increased by:

• Increasing the channel dopant concentration.
• Reducing the channel length
• Reducing the gate oxide thickness.
• Reducing the channel dopant concentration.

D. Reducing the channel dopant concentration.

41. Two identical FET’s each characterized by the parameters g_m and r_d are connected in parallel. The composite FET is then characterized by the parameters:  

• g_m/2 and 2 r_d
• g_m/2 and r_d/2
• 2 g_m and r_d/2
• 2 g_m and 2 r_d

C. 2 g_m and r_d/2

42. An n-channel JEET has I_DSS = 2 mA and V_p = –4 v. Its transconductance g_m ( in milli mho) for an applied gate-to-source voltage V_Gs of –2 V is:

• 0.25
• 1.0
• 0.75
• 0.5

D. 0.5

43. The V-I characteristic of an n-channel depletion FET drain–source output has:

• I_DS = 0 at V_GS = 0 V
• I_DS is independent of V_GS
• I_DS = positive maximum at V_GS = 0 V
• I_DS = negative maximum at V_GS = 0 V

C. I_DS = positive maximum at V_GS = 0 V

44. For an enhancement-type MOSFET the output V-I characteristic of has:

• Only an ohmic region
• An ohmic region at low voltage value followed by a saturation region at higher voltages
• Only a saturation region
• An ohmic region at large voltage values preceded by a saturation region lower voltage

B. An ohmic region at low voltage value followed by a saturation region at higher voltages

45. For an n-channel JFET, having drain–source voltage constant if the gate–source voltage is increased to more negative pinch-off would occur for:

• Saturation value of drain current
• High values of drain current
• Zero drain current
• Source current equal to the drain current

C. Zero drain current

46. For a junction FET in the pinch-off region, as the drain voltage is increased, the drain current:

• Becomes zero
• Abruptly decreases
• Abruptly increases
• Remains constant

D. Remains constant

47. Now a days in MOSFET’s the material used for the gate is:

• Heavily doped polycrystalline silicon
• Pure silicon
• High purity silica oxide
• Epitaxial grown silicon

A. Heavily doped polycrystalline silicon

48. An n-channel JFET has I_DS whose value is:

• Maximum for V_GS = 0, and minimum for V_GS = negative and large
• Minimum for V_GS = 0, and maximum for V_GS = negative and large
• Maximum for V_GS = 0, and minimum for V_GS = positive and large
• Minimum for V_GS = 0, and maximum for V_GS = positive and large

A. Maximum for V_GS = 0, and minimum for V_GS = negative and large

49. The threshold voltage of an n-channel enhancement mode MOSFET is 0.5 V. When the device is biased at a gate voltage of 3 V. Pinch-off would occur at a drain voltage of:

• 1 V
• 0.5 V
• 3.5 V
• 2.5 V

D. 2.5 V

50. Bipolar transistors are ____________ than field effect transistor.

• Less sensitive and slower
• More sensitive and faster
• More sensitive and slower
• Less sensitive and faster

A. Less sensitive and slower

51. The main factor, which differentiates a D-MOSFET from an E-MOSFET, in the absence of:

• p–n junction
• Insulated gate
• Electrons
• Channel

D. Channel

52. In order to protect a MOSFET against damage from any stray voltage at the gate:

• Grounding rings are provided
• Source terminal is earthen
• Terminals are shorted
• None

B. Source terminal is earthen

53. n-channel FET’s are superior to p-channel FET’s because:

• Mobility of electrons is smaller than that of holes
• Mobility of electrons is greater than that of holes
• They have high switching time
• They consume less power

B. Mobility of electrons is greater than that of holes

54. Pinch-off voltage V_p for an FET is the drain voltage at which:

• Drain current becomes zero
• All free charges get removed from the channel
• Significant drain current starts flowing
• Avalanche breakdown takes place

A. Drain current becomes zero

55. The transconductance g_m of a diffused JFET is the order of:

• 1 mS
• 1 S
• 100 S
• 1000 S

A. 1 mS

56. The gate-to-source resistance of an FET is of the order of:

• 100 MΩ
• 10 MΩ
• 1 MΩ
• 0.1 MΩ

D. 0.1 MΩ

57. Inter-electrode capacitances in an FET are of the order of:

• 1 pF
• 100 pF
• 0.1 µF
• 1 µF

A. 1 pF

58. FET has offset voltage of about:

• 0.2 V
• 0.6 V
• 1.5 V
• Zero

D. Zero

59. A JFET has a potential divider bias arrangement if the resistor between the gate and power supply terminal is removed. The JFET will:

• Continue to work as an amplifier
• Have a forward-bias gate w. r. t source
• Not work as an amplifier but as a switch
• Immediately burn out

A. Continue to work as an amplifier

60. Which of the following transistors is symmetrical in there structure?

• n–p–n transistor
• JFET
• p–n–p transistor
• MOSFET

D. MOSFET

61. The drain current in JFET is controlled by:

• Voltage drop across channel
• Depletion regions
• Channel resistance
• Reverse-bias at the gate

D. Reverse-bias at the gate

62. A JFET

• Is a voltage-controlled device
• Is a current-controlled device
• Has a low input resistance
• Has a very large voltage gain

A. Is a voltage-controlled device

63. A unipolar transistor uses

• Both free electrons and holes
• Only free electrons
• Only holes
• Either one or the other, but not both

D. Either one or the other, but not both

64. The input impedance of a JFET

• Approaches zero
• Approaches one
• Approaches infinity
• Is impossible to predict

C. Approaches infinity

65. The gate controls

• The width of the channel
• The drain current
• The proportional pinch-off voltage
• All the above

D. All the above

66. The gate-source diode of a JFET should be

• Forward-biased
• Reverse-biased
• Either forward- or reverse biased
• None of the above

B. Reverse-biased

67. Compared to a bipolar transistor, the JFET has a much higher

• Voltage gain
• Input resistance
• Supply voltage
• Current

B. Input resistance

68. The pinch-off voltage has the same magnitude as the

• Gate voltage
• Drain-source voltage
• Gate-source voltage
• Gate-source cutoff voltage

D. Gate-source cutoff voltage

69. When the drain saturation current is less than IDSS, a JFET acts like a

• Bipolar transistor
• Current source
• Resistor
• Battery

C. Resistor

70. RDS equals pinch-off voltage divided by the

• Drain current
• Gate current
• Ideal drain current
• Drain current for zero gate voltage

D. Drain current for zero gate voltage

71. The transconductance curve is

• Linear
• Similar to the graph of a resistor
• Nonlinear
• Like a single drain curve

C. Nonlinear