MCQ on Electronic Devices & Circuits

 Diode & their applications:

1. In a PN junction with no external voltage, the electric field between acceptor and donor ions is called a:
A. Peak B. Barrier C. Threshold D. Path
Answerb
2. In a PN junction the potential barrier is due to the charges on either side of the junction, these charges are
A. Majority carriers B. Minority carriers C. Both (a) and (b) D. Fixed donor and acceptor ions
Answerd
3. In an unbiased PN junction
A. The junction current is due to minority carriers only B. The junction current at equilibrium is
zero as equal but opposite carriers are crossing the junction C. The junction current reduces with rise
in temperature D. The junction current at equilibrium is zero as charges do not cross the junction
Answerb
4. When a PN junction is reverse-biased
A. Holes and electrons tend to concentrate towards the junction B. The barrier tends to break
down C. Holes and electrons tend to move away from the junction D. None of the above
Answerc
5. A PN junction
A. Has low resistance in forward as well as reverse directions B. Has high resistance in forward as well
as reverse directions C. Conducts in forward direction only D. Conducts in reverse direction only
Answerc
6. PN junction failure below 5 V is caused primarily by
A. Avalanche breakdown B. Zener breakdown C. Either of (a) and (b) above D. None of these
Answerb
7. The depletion layer of a PN junction diode has
A. Only free mobile holes B. Only free mobile electrons C. Both free mobile holes as well as
electrons D. Neither free mobile electrons nor holes
Answerd
8. The diode is used in
A. Digital circuits B. Detectors C. Rectifiers D. All of the above
Answerd
9. In a Zener diode with high breakdown voltage A. Both P and N are heavily doped B. Both P and N
are lightly doped C. Either P or N is lightly doped D. None of the above
Answerb
10. In Zener diode, the Zener breakdown takes place A. Above 6 V B. Below 6 V C. At 6 V D. None
of the above
Answerb
11. The current in a Zener diode is controlled by A. Zener diode resistance B. Potential barrier
C. Reverse bias voltage D. External circuits
Answerd
12. A zener diode when biased correctly A. Acts as a fixed resistance B. Never overheats C. Has a
constant voltage across it D. Has a constant current passing through it
Answerc
13. In a half wave rectifier, the load current flows for what part of the cycle. a. 400 b. 900 c. 1800 d. 3600
Answerc
14. In a full wave rectifier, the current in each diode flows for a. whole cycle of the input signal
b. half cycle of the input signal c. more than half cycle of the input signal d. none of these
Answerb
15. In a full wave rectifier, if the input frequency is 50 Hz, then output frequency will be a. 50 Hz
b. 75 Hz c. 100 Hz d. 200 Hz Answerc
16. In a center tap full wave rectifier, if Vm is the peak voltage between center tap and one end of the
secondary, the maximum voltage coming across the reverse bias diode is
a. Vm b.2 Vm c. Vm/2 d. Vm/√2 Answerb
17. The maximum efficiency of full wave rectification is a. 40.6% b. 100% c. 81.2%
d. 85.6% Answerc
18. In a bridge type full wave rectifier, if Vm is the peak voltage across the secondary of the transformer, the
maximum voltage coming across each reverse biased diode is a. Vm b. 2 Vm c. Vm/2
d. Vm/√2 Answera
19. To get a peak load voltage of 40V out of a bridge rectifier. What is the approximate rms value of
secondary voltage? a. 0 V b. 14.4 V c. 28.3 V d. 56.6 V Answerc
20. If the line frequency is 50 Hz, the output frequency of bridge rectifier is a. 25 Hz b. 50 Hz
c. 100 Hz d. 200 Hz Answerc
21. The ripple factor of a bridge rectifier is a. 0.482 b. 0.812 c. 1.11 d. 1.21
Answera
22. The bridge rectifier is preferred to an ordinary two diode full wave rectifier because a. it needs much
smaller transformer for the same output b. no center tap required c. less PIV rating per
diode d. all the above Answerd
23. The basic purpose of filter is to a. minimize variations in ac input signal b. suppress
harmonics in rectified output c. remove ripples from the rectified output d. stabilize dc
output voltage Answerc
24. The use of a capacitor filter in a rectifier circuit gives satisfactory performance only when the load
a. current is high b. current is low c. voltage is high d. voltage is low Answerb
25. A half wave rectifier is equivalent to a. clamper circuit b. a clipper circuit c. a clamper
circuit with negative bias d. a clamper circuit with positive bias Answerb
26. In a LC filter, the ripple factor, a. Increases with the load current b. increases with the load
resistance c. remains constant with the load current d. has the lowest value Answerc
27. The basic reason why a full wave rectifier has a twice the efficiency of a half wave rectifier is that
a. it makes use of transformer b. its ripple factor is much less c. it utilizes both half-
cycle of the input d. its output frequency is double the line frequency Answerc
 BJT & its biasing:

28. A transistor has how many doped regions? a. 1 b. 2 c. 3 d. 4 Answer: c

29. What is one important thing transistors do? a. Amplify weak signals b. Rectify line voltage
C. Regulate voltage d. Emit light Answer: a
30. The emitter diode is usually a. Forward-biased b. Reverse-biased
c. Non conducting d. Operating in the breakdown region Answer: a
31. For normal operation of the transistor, the collector diode has to be a. Forward-biased
b. Reverse-biased c. Non-conducting d. Operating in the breakdown region
Answer: b
32. The base of an npn transistor is thin and a. Heavily doped b. Lightly doped
c. Metallic d. Doped by a pentavalent material Answer: b
33. When a free electron recombines with a hole in the base region, the free electron becomes
a. Another free electron b. A valence electron c. A conduction-band electron
d. A majority carrier Answer: b
34. What is the most important fact about the collector current? a. It is measured in milliamperes.
b. It equals the base current divided by the current gain. c. It is small.
d. It approximately equals the emitter current. Answer: d
35. The power dissipated by a transistor approximately equals the collector current times a. Base-emitter
voltage b. Collector-emitter voltage c. Base supply voltage d. 0.7 V Answer: b
36. A small collector current with zero base current is caused by the leakage current of the a. Emitter
diode b. Collector diode c. Base diode d. Transistor Answer: b
37. A transistor acts like a diode and a a. Voltage source b. Current source c. Resistance
d. Power supply Answer: b
38. If the base current is 100 mA and the current gain is 30, the collector current is a. 300 mA
b. 3 A c. 3.33 A d. 10 A Answer: b
39. . If the base resistor is open, what is the collector current? a. 0 b. 1 mA
c. 2 mA d. 10 mA Answer: a
40. A current ratio of IC/IE is usually less than one and is called: A. Beta B. Theta
C. Alpha D. Omega A nswer: Option C
41. Which is beta's current ratio? A. IC / IB B. IC / IE C. IC / IE D. IE / IB Answer: Option
A
42. In a transistor, collector current is controlled by: A. collector voltage B. base current
C. collector resistance D. all of the above Answer: Option B
43. Total emitter current is: A. IE – IC B. IC + IE C. IB + IC D. IB – IC Answer:
Option C
44. In CB Configuration of transistor, the input impedance is A. High B. Medium C. Low
D. none of these Answer: Option C
45. BJT is ———–Device A. Bipolar B. Unipolar C. Constant current
D. Constant voltage Answer: Option A
46. Transistor is used as A. Switch B. Amplifier C. Both (a) & (b) D. None of these
Answer: Option C
47. For a common emitter circuit if IC/IE = 0.98 then current gain for common emitter circuit will be
A.49 B. 98 C. 4.9 D. 25.5 Answer: Option A
48. In a transistor highly doped part is A. Emitter B. Base C. Collector
D. None of the above Answer: Option A
49. In a transistor lightly doped part is A. Emitter B. Base C. Collector D. None of the
above Answer: Option B
50. In a transistor largest dimension is that of A. Emitter B. Base C. Collector D. None
of the above Answer: Option c
51. .........is the region of transistor which has highest conductivity A. Base B. Emitter
C. Collector D. Any of the above Answer: Option B
52. A notch or a tab the transistor cap denotes A. Emitter pin B. Base pin C. Collector pin
D. None of the above Answer: Option a
53. Transistor works as an open switch when emitter junction is........biased and collector junction
is........biased A. Forward, reverse B. Reverse, reverse C. Reverse,
forward D. Forward, forward Answer: Option B
54. Transistor works as an closed switch when emitter junction is........biased and collector junction
is........biased A. Forward, reverse B. Reverse, reverse C. Reverse, forward
D. Forward, forward Answer: Option D

 Power Amplifiers:

55. The output stage of a multistage amplifier is also called …………… 1. Mixer stage 2. Power
stage 3. Detector stage 4. F stage Answer: 2
56. ………………. coupling is generally employed in power amplifiers 1. Transformer 2. RC
3. Direct 4. Impedance Answer: 1
57. A class A power amplifier uses ………… 1. Two transistors 2. Three transistors
3. One transistor 4. None of the above Answer: 3
58. The maximum efficiency of resistance loaded class A power amplifier is …….. 1. 5% 2. 50%
3. 30% 4. 25% Answer: 4
59. The maximum efficiency of transformer coupled class A power amplifier is ……………… 1. 30%
2. 50% 3. 80% 4. 45% Answer: 2
60. Class……. power amplifier has the highest collector efficiency: 1. C 2. A
3. B 4. AB Answer: 1
61. Power amplifiers handle …………. signals compare to voltage amplifiers 1. Small
2. Very small 3. Large 4. None of the above Answer: 3
62. In class A operation, the operating point is generally located ………. of the d.c. load line. 1. At cut
off point 2. At the middle 3. At saturation point 4. None of these
Answer: 2
63. A power amplifier has comparatively …………….. β 1. Small 2. Large 3. Very large
4. None of these Answer: 1
64. The maximum collector efficiency of class B operation is …………….. 1. 50% 2. 90% 3. 5%
4. 5% Answer: 4
65. A 2-transistor class B power amplifier is commonly called ……….. amplifier 1. Dual 2. Push-
pull 3. Symmetrical 4. Differential Answer: 2
66. The output stage of a multistage amplifier usually employs ……….. 1. Push-pull amplifier
2. Preamplifier 3. Class A power amplifier 4. None of these Answer: 1
67. The output transformer used in a power amplifier is a ……………. transformer 1. 1:1 ratio
2. Step-up 3. Step-down 4. None of these Answer: 3

 JFET & MOSFET:

68. A JFET has three terminals, namely ………… 1. cathode, anode, grid 2. emitter, base, collector
3. source, gate, drain 4. none of these Answer: 3
69. A JFET is similar in operation to …………. valve 1. Diode 2. pentode 3. triode
4. tetrode Answer: 2
70. A JFET is also called …………… transistor 1. unipolar 2. bipolar 3. unijunction 4. none
of the above Answer: 1
71. A JFET is a ………… driven device 1. current 2. voltage 3. both current and
voltage 4. none of the above Answer: 2
72. The gate of a JFET is ………… biased 1. Reverse 2. Forward
3. reverse as well as forward 4. none of these Answer: 1
73. The input impedance of a JFET is …………. that of an ordinary transistor 1. equal to 2. less
than 3. more than 4. none of these Answer: 3
74. In a p-channel JFET, the charge carriers are ………….. 1. electrons 2. holes
3. both electrons and holes 4. none of these Answer: 2
75. When drain voltage equals the pinch-off-voltage, then drain current …………. with the increase in drain
voltage 1. decreases 2. increases 3. remains constant 4. None Answer: 3
76. A MOSFET has …………… terminals 1. Two 2. five 3. four 4. three
Answer: 4
77. A MOSFET can be operated with …………….. 1. negative gate voltage only 2. positive gate voltage
only 3. positive as well as negative gate voltage 4. none Answer: 3
78. A JFET has ……….. power gain 1. small 2. very high 3. very small
4. none of the above Answer: 2
79. The input control parameter of a JFET is …………… 1. gate voltage 2. source voltage
3. drain voltage 4. gate current Answer: 1
80. The two important advantages of a JFET are ………….. 1. high input impedance and square-law property
2. inexpensive and high output impedance 3. low input impedance and high output impedance
4. none of these Answer: 1
81. A MOSFET is sometimes called ………. JFET 1. many gate 2. open gate 3. insulated gate
4. shorted gate Answer: 3
82. Which of the following devices has the highest input impedance? 1. JFET 2. MOSFET
3. Crystal diode 4. ordinary transistor Answer: 2
83. A MOSFET uses the electric field of a ………. to control the channel current 1. capacitor 2. battery
3. generator 4. none of the above Answer: 1
84. The input impedance of a MOSFET is of the order of ……….. 1. Ω 2. a few hundred Ω
3. kΩ 4. several MΩ Answer: 4
85. For VGS = 0 V, the drain current becomes constant when VDS exceeds ……… 1. cut off 2. VDD
3. VP 4. 0 V Answer: 3
86. D-MOSFETs are sometimes used in series to construct a cascade high frequency amplifier to overcome
the loss of ………….. 1. low output impedance 2. capacitive reactance 3. high input impedance
4. inductive reactance Answer: 3
87. IDSS can be defined as ……… 1. the minimum possible drain current 2. the maximum possible
current with VGS held at –4 V 3. the maximum possible current with VGS held at 0 V
4. the maximum drain current with the source shorted Answer: 3
88. The input impedance of a common-gate configured JFET is ………… 1. very low 2. low
3. high 4. very high Answer: 1
89. A very simple bias for a D-MOSFET is called …….. 1. self biasing 2. gate biasing 3. zero
biasing 4. voltage-divider biasing Answer: 3
90. With the E-MOSFET, when gate input voltage is zero, drain current is ….. 1. at saturation
2. Zero 3. IDSS 4. widening the channel Answer: 2
91. When VGS = 0 V, a JFET is………. 1. Saturated 2. an analog device 3. an open switch
4. an open switch Answer: 1
92. The electrons flow through a p-channel JFET from ……….. to ………….. 1. from source to drain
2. from source to gate 3. from drain to gate 4. from drain to source Answer: 4
93. Which component is considered to be an “OFF” device . 1. Transistor 2. JFET
3. D-MOSFET 4. E-MOSFET Answer: 4
94. A FET is a...........controlled device whereas a bipolar transistor is a............controlled device.
A. Current, voltage B. Drain, gate C. Gate, drain D. Voltage, current Answer:
Option D
95. FET acts as constant current source in A. Ohmic region B. Breakdown region
C. Pinch off region D. Both (b) and (c) Answer: Option A
96. The gate input current of a FET is of the order of A. Amperes B. Microamperes
C. Miliamperes D. Hundreds of nano amperes Answer: Option D