ANALOG AND POWER ELECTRONICS 119 IMPORTANT EXPECTED MCQ PDF FOR VIZAG MT & BEL PE EXAM 2017

1. The conventional current in a PN junction diode
flows: 

(a) From positive to negative
(b) From negative to positive
(c) In the direction opposite to the electron flow.
d) Both (a) and (c) above
Answer-A
2. The cut in voltage (or knee voltage) of a silicon diode is
(a) 0.2V (b) 0.7V (c) 0.8 V (d) 1.0V
Answer-B
3. When a diode is reverse biased, it is equivalent to
(a) An OFF switch     (b) an ON switch
(c) A high resistance (d) none of the above
Answer-A
4. The resistance of a diode is equal to
(a) Ohmic resistance of the P- and N- semiconductors
(b) Junction resistance
(c) Reverse resistance
(d) Algebraic sum of (a) and (b) above
Answer-D
5. For a silicon diode, the value of the forward – bias voltage typically
(a) Must be greater than 0.3V
(b) Must be greater than 0.7V
(c) Depends on the width of the depletion region
(d) Depends on the concentration of majority carriers
Answer-B
6. When forward biased, a diode
(a) Blocks current            (b)
conducts current
(c) Has a high resistance (d) drops a large voltage.
Answer-B
7. A PN junction diode’s dynamic conductance is directly proportional to
(a) The applied voltage (b) the temperature
(c) The current              (d) the
thermal voltage
Answer-C
8. The forward region of a semiconductor diode characteristic curve is where
diode appears as
(a) Constant current source (b) a capacitor
(c) An OFF switch (d) an ON switch
Answer-D
9. At room temperature of 25 °C, the barrier potential for silicon is 0.7 V.
lts value at 125° C is
(a) 0.5V (b) 0.3V (c) 0.9V (d) 0.7V
Answer-A
10. Junction breakdown of a PN junction occurs
(a) With forward bias (b) with reverse bias
(c) Because of manufacturing defect (d) none of these
Answer-B
11. Reverse saturation current in a silicon PN junction diode nearly doubles
for every
(a) 2° C rise in temperature (b) 5° C rise in temperature
(c) 6° C rise in temperature (d) 10° C rise in temperature
Answer-D
12. An electron has
(a) positive charge (b) Negative Charge (c) Neutral (d) none
Answer-B
13. The element that does not have three valance electrons is
(a) Boron (b) Aluminum (c) Germanium (d) Gallium
Answer-C
14. The donor impurity element is
(a) Aluminum (b) Boron (c) Phosphorous (d) Indium
Answer-C
15. The acceptor impurity element is
(a) Antimony (b) Gallium (c) Arsenic (d) Phosphorous
Answer-B
16. The most important Application of Diode is as a
(a) Rectifier                              (b) Switching
Device
(c) Voltage Controlled Device (d) both (a) and (b)
Answer-D
17. The Forbidden Energy gap for Silicon is
(a) 1.12eV (b) 0.32 eV (c) 0.72 eV (d) 0.71 Ev
Answer-D
18. When a diode is forward biased the
(a) Barrier potential increases (b) Barrier potential decreases
(c) Majority current decreases (d) Minority current decreases
Answer-B
19. When the reverse bias is applied junction diode it
(a) Lowers the potential barrier (b) rises the potential barrier
(c) Greatly decrease the minority carrier current
(d) Greatly increase the minority carrier current
Answer-B
20. Zener breakdown occurs
(a) Due to normally generated minority carriers (b) In lightly doped junctions
(c) Due to rupture of covalent bonds (d) Mostly in germanium junctions.
Answer-C
21. In Zener and Avalanche breakdown diodes the current flow is due to
(a) Majority Carriers
(b) Minority Carriers
(c) Majority and Minority Carriers
(d) None of these
Answer-B
22. Which of the following is not a semiconductor
(a) Gallium Arsenide (b) Indium (c) Germanium (d) Silicon
Answer-B
23. For a Germanium PN Junction diode, the maximum value of barrier Potential
is
(a) 0.3 V (b) 0.7 V (c) 1.3 V (d) 1.7 V
Answer-A
24. The depletion region in a PN Junction diode is due to
(a) Reverse biasing (b) Forward biasing
(c) Area Created by Crystal doping (d) an area void of current carriers
Answer-D
25. When holes leave the P-Material to fill electrons in the N-Material the
process is called
(a) Mixing (b) Depletion (c) Diffusion (d) None
Answer-C
26. There are two semiconductor diodes A & B.One of them is Zener where as
Other is
Avalanche. Their ratings are 5.6V & 24V respectively then.
(a) A is Zener B is Avalanche (b) A is Avalanche B is Zener
(c) both of them are Zener Diodes (d) both of them are Avalanche Diodes
Answer-A
27. The Breakdown that occurs in the Reverse biased condition in a narrow
junction Diode is
(a) Zener Breakdown (b) Avalanche Breakdown (c) Both a &b (d) None of these
Answer-A
28. The Breakdown that occurs in the Reverse biased condition in a wider
junction Diode is
(a) Zener Breakdown (b) Avalanche Breakdown (c) Both a &b (d) None of these
Answer-B
29. The capacitance appearing across a reverse biased semiconductor junction
a) increases with increase in bias voltage
b) decreases with increase in bias voltage
c) is independent of bias voltage
d) none of these
Answer-B
30. A breakdown which is caused by cumulative multiplication of carriers
through filed induced
impact ionization occurs in
a) Zener diode b) Tunnel diode c) Varactor diode d) avalanche diode
Answer-D
31. For a highly doped diode
a) Zener breakdown is likely to take place
b) avalanche breakdown is likely to take place
c) either a) or b) will take place
d) neither a) or b) will take place
Answer-A
32. Forward bias résistance of ideal diode is
a) 10 ohms b) 1M ohms c)Infinity d) zero
Answer-D
33. In a semiconductor diode, V-I relationship is such that
a) current varies linearly with voltage
b) current varies exponentially with voltage
c) current varies inversely with voltage
d) none of these
Answer-B
34. Reverse bias resistance of ideal diode is
a) 10 ohms b) 1M ohms c)Infinity d) zero
Answer-C
35. Emission coefficient of silicon (η) is
a) 0    b) 1   c) 2   d)
None
Answer-C
36. Under normal operating Voltage, Reverse current in a Silicon diode is about
a) 10mA
b) 1μA
c) 1000μA
d) None
Answer-B
37. A PN junction Diode
a) has high resistance in both forward and reverse directions
b) has low resistance in the forward direction
c) has high resistance in the forward direction
d) has low resistance in the reverse direction
Answer-B
38. Emission coefficient of Germanium (η) is
a) 0    b) 1   c) 2  d)
None
Answer-B
39. The static resistance of a Diode is
a) its opposes the D.C current flow
b) its opposes the A.C current flow
c) resistance of the diode when forward bias
d) none
Answer-A
40. In a PN junction, the potential barrier is due to the charges on either
side of the junction, which
consists of
a) fixed Donor and Acceptor ions
b) majority carriers only
c) minority carriers only
d) both majority &minority carriers
Answer-A
41. To Compensate increase in diode current with temperature, the diode voltage

a) Decreases by 2.5mV per 1°C
b) Increases by 2.5mV per 1°C
c) Decreases by 2.5mV per 10°C
d) Increases by 2.5mV per 10°C
Answer-A
42. If a PN junction diode is not biased, junction current at equilibrium is
a) zero as no charges cross the junction
b) zero as equal no. of carriers cross the barrier
c) mainly due to diffusion of majority carriers
d) mainly due to diffusion of minority carriers
Answer-B
43. The capacitance that exists in a forward biased junction is called
a) Diffusion capacitance
b) Transition capacitance
c) Space charge capacitance
d) Depletion region capacitance
Answer-A
44. Diffusion capacitance is given by
a) τI/ηVT
b) τVT/ηI
c) τηI/VT
d) τVTI/η
Answer-A
45. Reverse Saturation current increases by________ every 1°C rise in
temperature
a) 6%    b) 7%   c) 8%   d)
9%
Answer-B
46. A silicon diode has saturation current of 7.5μA at 300K.The saturation
current at 400K is
a) 7.68mA
b) 7.86mA
c) 7.68μA
d) 7.86μA
Answer-A
47. The value of forward current incase of a silicon PN diode with Io =10μA and
VF=0.8V at
T=300K is
a) 48.02A
b) 48.20A
c) 48.02mA
d) 48.20mA
Answer-A
48. The forward resistance of a Silicon PN diode when the forward current is
5mA at T=300K is
a) 10.34Ohm
b) 10.43Ohm
c) 10.50Ohm
d) 10.15Ohm
Answer-A
49. Applying an external D.C supply to an Electronic component is called 
a) Biasing
b) Aliasing
c) Diffusion
d) none
Answer-A
50. A Zener diode
(a) has a high forward-voltage rating
(b) has a sharp breakdown at low reverse voltage
(c) is useful as an amplifier
(d) has a negative resistance
Answer-B
51. The most important Application of Tunnel Diode is as a
(a) Rectifier (b) Switching Device (c) Voltage Controlled Device (d) none
Answer-B
52. A tunnel- diode is
(a) a very heavily-doped PN junction diode
(b) a high resistivity PN junction diode
(c) a slow switching device
(d) used with reverse bias
Answer-A
53. The light-emitting diode (LED)
(a) is usually made from silicon
(b) uses a reverse-biased junction
(c) gives a light output which increases with the increase in temperature
(d) depends on the recombination of holes and electrons
Answer-D
54. LED’s do not require
(a) heating                          (b)
warm-up time
(b) Both (a) and (b) above (d) non of above
Answer-C
55. The sensitivity of a photodiode depends upon
(a) light intensity and depletion region width
(b) depletion region width and excess carrier life time
(c) Excess carrier life time and forward bias current.
(d) Forward bias current and light intensity.
Answer-A
56. LEDs are commonly fabricated from gallium compounds like gallium arsenide
and gallium
phosphide because they
(a) Are cheap (b) are easily available
(c) Emit more heat (d) emit more light.
Answer-D
57. A LED is basically a _______________ P-N junction.
(a) forward-biased (b) reverse-biased
(c) lightly-doped (d) heavily-doped
Answer-A
58. As compared to a LED display, the distinct advantage of an LCD display is
that it requires
(a) No illumination (b) extremely-bias
(c) No forward-bias (d) a solid crystal
Answer-B
59. Before illuminating a P-N junction photodiode, it has to be
(a) Reverse-biased (b) forward-biased
(c) Switched ON (d) switched OFF.
Answer-A
60. A LED emits visible light when its ______________
(a) P-N junction is reverse-biased (b) depletion region widens
(c) Holes and electrons recombine (d) P-N junction becomes hot.
Answer-C
61. In LED, light is emitted because
(a) Recombination of charge carriers takes place
(b) Diode gets heated up
(c) Light falling on the diode gets amplified
(d) Light gets reflected due to lens action.
Answer-A
62. GaAs, LEDs emit radiation in the
(a) Ultraviolet region (b) violet – blue green range of the visible region
(c) Visible region (d) infra-red region
Answer-D
63. In a half – wave rectifier, the load current flows for
(a) Complete cycle of the input signal
(b) Less than half-cycle of the input signal,
(c) More than half-cycle but less than complete cycle of the input signal.
(d) Only for the positive half-cycle of the input signal.
Answer-D
64. In a full-wave rectifier, the current in each of the diodes flows for
(a) Complete cycle of the input signal. (b) Half cycle of the input signal.
(c) Less than half of the input signal. (d) None of the above.
Answer-B
65. The ripple factor of a bridge rectifier is
(a) 0.482 (b) 0.812 (c) 1.11 (d) 1.21
Answer-A
66. The ripple factor of a Half Wave rectifier is
(a) 0.482 (b) 0.812 (c) 1.11 (d) 1.21
Answer-D
67. A bridge rectifier is preferable to an ordinary two-diode full-wave
rectifier because
(a) It needs much smaller transformer for the same output.
(b) It uses four diodes.
(c) Its transformer does not require center-tap.
(d)None of the above.
Answer-C
68. The basic purpose of a filter is to
(a) Minimize variations in a.c. input signal.
(b) Suppress harmonics in rectified output.
(c) Remove ripples from the rectified output.
(d) Stabilize D.C. output voltage.
Answer-C
69. 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
Answer-B
70. A half-wave rectifier is equivalent to a
(a) a clamper circuit (b) a clipper circuit
(c) a clamper circuit with negative bias (d) a clamper circuit with positive
bias
Answer-B
71. Bridge rectifiers are preferred because
(a) they require small transformer
(b) they have less peak-inverse voltage
(c) they need small transformer and also have less peak-inverse voltage
(d) They have low ripple factor.
Answer-C
72. 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.
Answer-C
73. The output of a half-wave rectifier is suitable only for
(a) Running car radios (b) running a.c. motors
(c) Charging batteries (d) running tape recorders.
Answer-B
74. The ripple factor of a full wave rectifier is
(a) 0.48 (b) 0.812 (c) 1.21 (d) 1.11
Answer-A
75. The disadvantage of a bridge rectifier is 
(a) Its PIV is 2Vm
(b) It has 81.2% efficiency
(c) It has 4 diodes
(d) None
Answer-C
76. In a rectifier, larger the value of shunt capacitor filter
(a) larger the peak-to-peak value of ripple voltage
(b) larger the peak current in the rectifying diode
(c) longer the time that current pulse flows through the diode
(d) Smaller the d.c. voltage across the load.
Answer-B
77. 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.
Answer-C
78. The main reason why a bleeder resistor is used in a d.c. power supply is
that it
(a) Keeps the supply ON (b) improves voltage regulation
(c) Improves filtering action (d) both (b) and (c)
Answer-D
79. Which rectifier requires four diodes?
(a) half-wave rectifier. (b) full-wave rectifier.
(c) both a) and b) (d) bridge rectifier.
Answer-D
80. If, by mistake, a.c source in a bridge rectifier, is connected across the
d.c. terminals, it will burn out
and hence short _____________ diodes.
(a) one (b) two (c) three (d) four
Answer-D
81. The d.c. output polarity from a half-wave rectifier can be reversed by
reversing
(a) The diode (b) transformer primary
(c) Transformer secondary (d) both (b) and (c)
Answer-A
82. In a half-wave rectifier if a resistance equal to load resistance is
connected in parallel with the diode,
then
(a) Output voltage would be halved (b) output voltage would be doubled
(c) Circuit will stop rectifying (d) output voltage will remain unchanged,
Answer-C
83. If the input supply frequency is 50 Hz, the output ripple frequency of a
bridge rectifier is ________
Hz.
(a) 100 (b) 75 (c) 50 (d) 25.
Answer-A
84. TUF is maximum for
(a) Half-wave rectifier (b) Full-wave rectifier
(c) Bridge rectifier (d) Both a) and b)
Answer-C
85. The ripple frequency for a full wave rectifier is
(a) Equal to the supply frequency (b) twice the supply frequency
(c) Thrice the supply frequency (d) None
Answer-B
86. T .U.F for half wave rectifier is
(a) 0.963 (b) 0.693 (c) 0.287 (d) 0.278
Answer-C
87. T.U.F for full wave rectifier is
(a) 0.963 (b) 0.693 (c) 0.369 (d) 0.639
Answer-B
88. Form factor of the full wave rectifier is
(a) 1.57 (b) 1.21 (c) 1.11 (d) 2.71
Answer-C
89. Form factor of the half wave rectifier is
(a) 1.57 (b) 1.21 (c) 1.11 (d) 2.71
Answer-A
90. The efficiency of the bridge rectifier is
(a) 40.6 % (b) 81.2 % (c) 1.12 % (d) 48.2 %
Answer-B
91. An SCR conducts appreciable current when its —–with respect to cathode
(a) Anode and gate are both negative
(b) Anode and gate are both positive
(c) Anode is negative and gate is positive
(d) Anode is positive and gate is negative
Answer-B
92. The ripple factor in a C-filter decreases with
(a) Decrease in C (b) Increase in C (c) Decrease in RL (d) Decrease in f
Answer-B
93. The ripple factor in a L-filter increases with
(a) Decrease in RL (b) Increase in L (c) Increase in RL (d) Increase in f
Answer-C
94. An SCR may be turned OFF by
(a) Interrupting its anode current
 (b) reversing
polarity of its anode-cathode voltage
(b) low-current dropout
(c) all of the above
Answer-D
95. The “cut-in” voltage of a silicon
small-signal transistor is
(a) 0V (b) 0.2V (c) 0.5V (d) 0.7V
Answer-D
96. When the collector junction in transistors is biased in the reverse
direction and the emitter junction in
the forward direction, the transistor is said to be in the
(a) Active region (b) cut-off region
(c) Saturation region (d) none of them.
Answer-A
97. The transistor is said to be in saturation region when
(a) both collector and emitter junctions are forward biased
(b) both collector and emitter junctions are reversed biased ·
(c) emitter junction is forward biased, but the collector junction is reverse
biased
(d) emitter junction is reverse biased, but the collector junction is forward
biased
Answer-A
98. In a NPN transistor, when the emitter junction is reverse biased and the
collector junction is reverse
biased the transistor will operate in the
(a) Active region (b) Saturation region (c) Cut-off region (d) Inverted region
Answer-C
99. A conducting bipolar transistor dissipates least power when operating in
the
(a) Saturation region (b) Cut-off region (c) Active region (d) Reverse Active
region
Answer-A
100. For NPN transistor the N regions are
(a) Emitter and Base (b) Base and Collector (c) Emitter and Collector (d) None
Answer-C
101. A Collector collects
(a) Electrons from the base in case of PNP transistors
(b) Electrons from the emitter in case of PNP transistors
(c) holes from the base in case of NPN transistors
(d) holes from the base in case of PNP transistors
Answer-D
102. In a PNP transistor with normal bias
(a) collector junction has negligible resistance
(b) only holes cross collector junction
(c) collector base junction is reverse biased and emitter base junction is
forward biased
(d) only majority carriers cross the collector junction
Answer-C
103. A PNP transistor is made of
(a) Silicon
(b) Germanium
(c) either silicon or germanium
(d) none
Answer-C
104. In most transistors,collector is made physically larger than Emitter
region
(a) for dissipating heat
(b) to distinguish it from other regions
(c) as it is sensitive to UV rays
(d) to reduce resistance in the path of flow of electrons
Answer-A
105. The three terminals of a Bipolar transistor are called
(a) Anode,Cathode and Gate
(b) Anode,Emitter and Gate
(c) Emitter,Base and Collector
(d) None
Answer-C
106. In an NPN transistor, the arrow indicates current flow from
(a) Emitter to Base
(b) Base to Emitter
(c) Emitter to collector
(d) None.
Answer-B
107. For a operation of PNP amplifier, base of the Amplifier must be
(a) 0V
(b) positive with respect to collector
(c) negative with respect to collector
(d) greater than collector current
Answer-B
108. In a transistor the region that is very lightly doped and very thin is the

(a) emitter
(b) base
(c) collector
(d) none
Answer-B
109. In an NPN transistor,the Emitter
(a) emits or injects holes into the collector
(b) emits or injects electrons into the collector
(c) emits or injects electrons into the base
(d) emits or injects holes into the base
Answer-B
110. In an PNP transistor, with normal bias, the Emitter junction
(a) is always Reverse biased
(b) offers very high resistance
(c) offers very low resistance
(d) remains open
Answer-C
111. In a PNP transistor, electrons flow
(a) into the transistor at the collector only
(b) into the transistor at the base and collector leads
(c) out of the transistor at the base and collector leads
(d) out of the transistor at the base, collector as well as emitter leads
Answer-B
112. The arrow head on a transistor symbol indicates
(a) direction of Electron current in the Emitter
(b) direction of hole current in the Emitter
(c) diffusion current in the emitter
(d) drift current in the emitter
Answer-A
113. The largest current flow of a bipolar transistor occurs
(a) in emitter
(b) in base
(c) in collector
(d) through emitter-collector
Answer-A
114. Conventional biasing of a bipolar transistor has
(a) EB forward biased and CB forward biased
(b) EB reversed biased and CB forward biased
(c) EB forward biased and CB reverse biased
(d) EB reversed biased and CB reverse biased
Answer-C
115. In an PNP transistor, the arrow indicates current flow from
(a) Base to Emitter
(b) Emitter to Base
(c) Emitter to collector
(d) None.
Answer-B
116. In a normally biased NPN transistor, the main current crossing the
collector junction is
(a) a drift current
(b) a hole current
(c) a diffusion current
(d) same as base current
Answer-A
117. The bipolar junction transistor can be considered as
(a) two back to back connected diodes
(b) two diodes connected in parallel
(c) both a) and b)
(d) none
Answer-A
118. ICO in a diode and ICBO in a transistor mainly consist of
(a) majority carriers
(b) minority carriers
(c) both a) and b)
(d) none
Answer-B
119. The operation of transistor depends on
(a) interaction of both minority and majority carriers
(b) majority carriers only
(c) minority carriers only
(d) none
Answer-A
 

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