1. Consider a zener diode with a slope resistance of 10 Ω in series with a 90 Ω resistor fed from a dc supply containing a ripple voltage of 20mV peak-to-peak. Compute for the ripple voltage in load
Correct : B. 2 mv p-p
2. The of a common collector configuration is unity
Correct : A. voltage gain
3. Transmit time is the time taken by the electrons on holes to pass from
Correct : A. emitter to collector
4. Which amplifier is commonly used as a frequency multiplier?
Correct : C. class c
5. A class A amplifier has a voltage gain of 30 and a current gain of
What is the power gain?
Correct : D. 750
6. You have an application for a power amplifier to operate on FM radio frequencies. The most likely choice would be a amplifier.
Correct : C. class c
7. A class A amplifier with RC = 3.3 kΩ and RE = 1.2 kΩ has a VCC = 20 V. Find IC(sat).
Correct : A. 4.4 ma
8. A class C amplifier has a tank circuit in the output. The amplifier is conducting only 28°. The output voltage is
Correct : C. a sine wave.
9. In practice, the efficiency of a capacitively coupled class A amplifier is about %.
Correct : D. 10
10. The Q-point is at cutoff for class operation.
Correct : B. b
11. Class amplifiers are normally operated in a push-pull configuration in order to produce an output that is a replica of the input.
Correct : D. ab
12. The maximum efficiency of a class B amplifier is percent.
Correct : D. 79
13. A class amplifier is biased slightly above cutoff and operates in the linear region for slightly more than 180º of the input cycle.
Correct : D. ab
14. Which class of amplifier operates in the linear region for only a small part of the input cycle?
Correct : C. c
15. The principal advantage(s) of MOSFETs over BJTs is (are)
Correct : D. all of the above
16. The principal advantage(s) of BJTs over MOSFETs is (are) that
Correct : C. both of the above
17. The class amplifier is biased below cutoff.
Correct : C. b
18. For Class-B operation, the collector current flows for
Correct : B. half the cycle
19. Transformer coupling is an example of
Correct : B. ac coupling
20. Class-C amplifiers are almost always
Correct : C. tuned rf amplifiers
21. Heat sinks reduce the
Correct : C. junction temperature
22. Which type of power amplifier is biased for operation at less than 180º of the cycle?
Correct : C. class c
23. What is the maximum efficiency of a class A circuit with a direct or series-fed load connection?
Correct : D. 25%
24. The Q-point is at cutoff for class operation.
Correct : B. b
25. Which of the following is (are) power amplifiers?
Correct : D. all of the above
26. The output of a class-B amplifier
Correct : B. consists of positive half cycle only
27. Crossover distortion occurs in amplifiers.
Correct : A. push-pull
28. The main use of a class C amplifier is
Correct : A. as an rf amplifier
29. The decibel is a measure of
Correct : D. sound level
30. The output stage of a multistage amplifier is also called
Correct : B. power stage
31. coupling is generally employed in power amplifiers
Correct : A. transformer
32. The maximum efficiency of resistance loaded class A power amplifier is
Correct : D. 25%
33. Class power amplifier has the highest collector efficiency
Correct : C. b
34. Power amplifiers handle signals compare to voltage amplifiers.
Correct : C. large
35. In class B operation, at what fraction of VCC should the level of VL(p) be to achieve the maximum power dissipated by the output transistor?
Correct : B. 0.636
36. In class A operation, the operating point is generally located
of the d.c. load line.
Correct : B. at the middle
37. The output transformer used in a power amplifier is a transformer.
Correct : C. step-down
38. Power amplifiers primarily provide sufficient power to an output load, typically from to .
Correct : D. a few w, tens of w
39. The main feature(s) of a large-signal amplifier is (are) the .
Correct : D. all of the above
40. In power amplifiers, the output signal varies for a full 360º of the cycle.
Correct : A. class a
41. In class B power amplifiers, the output signal varies for of the cycle.
Correct : B. 180º
42. amplifiers have the highest overall efficiency.
Correct : D. class d
43. Class D operation can achieve power efficiency of over .
Correct : A. 90%
44. The beta of a power transistor is generally .
Correct : C. less than 100
45. A form of class A amplifier having maximum efficiency of _ uses a transformer to couple the output signal to the load.
Correct : C. 50%
46. The reflected impedance seen from one side of the transformer to the other side is .
Correct : B. (n1/n2)2
47. In a class A transformer-coupled power amplifier, winding resistance of the transformer determine(s) the dc load line for the circuit.
Correct : B. the dc
48. The slope of the ac load line in the class A transformer-coupled transistor is .
Correct : C. –1/(a2rl)
49. The amount of power dissipated by the transistor is the of that drawn from the dc supply (set by the bias point) and the amount delivered to the ac load.
Correct : B. difference
50. A class A amplifier dissipates power when the load is drawing maximum power from the circuit.
Correct : A. the least
51. In a class A transformer-coupled amplifier, the the value of VCEmax and the the value of VCEmin, the the efficiency to (from) the theoretical limit of 50%.
Correct : B. larger, smaller, closer
52. In class B operation, the current drawn from a single power supply has the form of rectified signal.
Correct : A. a full-wave
53. The highest efficiency is obtained in class B operation when the level of VL(p) is equal to .
Correct : C. vcc
54. transistors can be used to build a class B amplifier.
Correct : C. both npn and pnp or nmos and pmos
55. The complementary Darlington-connected transistor for a class B amplifier provides output current and output resistance.
Correct : B. higher, lower
56. The fundamental component is typically any harmonic component.
Correct : A. larger than
57. In Fourier technique, any periodic distorted waveform can be represented by the fundamental and all harmonic components.
Correct : D. adding
58. Improvement in production techniques of power transistors have
.
Correct : D. all of the above
59. The greater the power handled by the power transistor, the
Correct : A. the higher
60. The has the hottest temperature in a power transistor.
Correct : C. junction
61. A heat sink provides thermal resistance between case and air.
Correct : B. a low
62. A power amplifier is limited to use at one fixed frequency.
Correct : C. class c
63. By how much does the output signal vary for a class AB power amplifier?
Correct : C. between 180º and 360º
64. Which type of amplifier uses pulse (digital) signals in its operation?
Correct : D. class d
65. Which of the power amplifiers has the lowest overall efficiency?
Correct : A. class a
66. Which of the following describe(s) a power amplifier?
Correct : D. all of the above
67. amplifiers primarily provide sufficient power to an output load to drive a speaker from a few watts to tens of watts.
Correct : B. power
68. The main features of a large-signal amplifier is the circuit's
.
Correct : D. all of the above
69. Categorize the power efficiency of each class of amplifier, from worst to best.
Correct : C. a, ab, b, d
70. What is the ratio of the secondary voltage to the primary voltage with the turn ratio in the winding
Correct : A. n2/n1
71. Calculate the effective resistance seen looking into the primary of a 20:1 transformer connected to an 8- Ω load.
Correct : A. 3.2 kΩ
72. What transformer turns ratio is required to match an 8-speaker load so that the effective load resistance seen at the primary is 12.8 k?
Correct : B. 40:01:00
73. Calculate the efficiency of a transformer-coupled class A amplifier for a supply of 15 V and an output of V(p) = 10 V.
Correct : B. 33.30%
74. The maximum efficiency of a transformer-coupled class A amplifier is .
Correct : B. 50%
75. How many transistors must be used in a class B power amplifier to obtain the output for the full cycle of the signal?
Correct : C. 2
76. Class B operation is provided when the dc bias leaves the transistor biased just off, the transistor turning on when the ac signal is applied.
Correct : A. true
77. Calculate the efficiency of a class B amplifier for a supply voltage of VCC = 20 V with peak output voltage of VL(p) = 18 V. Assume RL = 16 Ω.
Correct : C. 70.69%
78. Which of the following is (are) the disadvantage(s) of a class B complementary-symmetry circuit?
Correct : D. all of the above
79. nMOS and pMOS transistors can be used for class B.
Correct : A. true
80. Calculate the harmonic distortion component for an output signal having fundamental amplitude of 3 V and a second harmonic amplitude of 0.25 V.
Correct : D. 8.33%
81. Which of the following instruments displays the harmonics of a distorted signal?
Correct : B. spectrum analyzer
82. Which of the following instruments allows more precise measurement of the harmonic components of a distorted signal?
Correct : D. wave analyzer
83. What is the maximum temperature rating for silicon power transistors?
Correct : C. 150º to 200º
84. Which of the power amplifiers is not intended primarily for large- signal or power amplification?
Correct : C. class c
85. Determine what maximum dissipation will be allowed for a 70-W silicon transistor (rated at 25ºC) if derating is required above 25ºC by a derating factor of 0.6 W/ºC at a case temperature of 100º.
Correct : A. 25 w
86. A silicon power transistor is operated with a heat sink (θSA = 1.5ºC/W). The transistor, rated at 150 W (25ºC), has θJC = 0.5º C/W, and the mounting insulation has θCS = 0.6 ºC/W. What is the maximum power that can be dissipated if the ambient temperature is 50ºC and TJmax = 200 ºC?
Correct : C. 57.7 w
87. Which of the following transistors has been quite popular as the driver device for class D amplification?
Correct : D. mosfet
88. Kirchhoff's Voltage Law states that the total voltage around a closed loop must be
Correct : A. 0
89. The algebraic sum of in a network of conductors meeting at a point is zero.
Correct : B. currents
90. The theorem is a way to determine the currents and voltages present in a circuit that has multiple sources.
Correct : B. super position
91. The concept on which Superposition theorem is based is
Correct : D. linearity
92. Kirchhoff’s current law is applicable to only
Correct : A. junction in a network
93. Kirchhoff's voltage law is related to
Correct : D. both b & c
94. Superposition theorem can be applied only to circuits having
Correct : D. linear bilateral elements
95. The concept on which superposition theorem is based on
Correct : D. linearity
96. Node analysis can be applied for
Correct : C. both a & b
97. Mesh analysis is applicable for
Correct : A. planar networks
98. The superposition theorem is applicable to
Correct : D. current, voltage and power
99. Kirchhoff’s current law is applicable only to
Correct : A. junction in a network
100. Maximum power output is obtained from a network when the load resistance is equal to the output resistance of the network as seen from the terminals of the load". The above statement is associated with