Which of the power amplifiers has the lowest overall efficiency?
Class A
Class B or AB
Class C
Class D
Q.2.
By how much does the output signal vary for a class AB power amplifier?
360º
180º
Between 180º and 360º
Less than 180º
Q.3.
How many transistors must be used in a class B power amplifier to obtain the output for the full cycle of the signal?
0
1
2
3
Q.4.
Which type of power amplifier is biased for operation at less thanof the cycle?
Class A
Class B or AB
Class C
Class D
Q.5.
Quiescent power is the power dissipation of a transistor
with no signal input.
with no load.
under full load.
along the dc load line.
Q.6.
What is the maximum temperature rating for silicon power transistors?
50º to 80º
100º to 110º
150º to 200º
250º to 300º
Q.7.
What is the maximum efficiency of a class B circuit?
90%
78.5%
50%
25%
Q.8.
A class C amplifier has a tank circuit in the output. The amplifier is conducting only 28°. The output voltage is
0 V.
a dc value equal to VC
a sine wave.
a square wave with a frequency determined by the tank.
Q.9.
NMOS and pMOS transistors can be used for class B.
True
False
Q.10.
The class ________ amplifier is biased below cutoff.
A
AB
B
C
Q.11.
A class ________ amplifier is biased slightly above cutoff and operates in the linear region for slightly more thanof the input cycle.
A
B
C
AB
Q.12.
The maximum efficiency of a transformer-coupled class A amplifier is ________.
25%
50%
78.5%
63.6%
Q.13.
The maximum efficiency of a class B amplifier is ________ percent.
50
25
70
79
Q.14.
Which of the following is (are) the disadvantage(s) of a class B complementary-symmetry circuit?
It needs two separate voltage sources.
There is crossover distortion in the output signal.
It does not provide exact switching of one transistor off and the other on at the zero-voltage condition.
All of the above
Q.15.
In practice, the efficiency of a capacitively coupled class A amplifier is about ________%.
25
40
70
10
Q.16.
Which of the following transistors has been quite popular as the driver device for class D amplification?
BJT
FET
UJT
MOSFET
Q.17.
The least efficient amplifier among all classes is
class
class
class A
class
Q.18.
In a class AB amplifier, if the VBE drops are not matched to the diode drops or if the diodes are not in thermal equilibrium with the transistors, this can result in
a current mirror.
diode separation.
crossover distortion.
thermal runaway.
Q.19.
Which operation class is generally used in radio or communications?
A
B
AB
C
E. D
Q.20.
Calculate the efficiency of a transformer-coupled class A amplifier for a supply ofV and an output of V(p) =V.
25%
33.3%
50%
78.5%
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