Analog Circuits Questions and Answers – Comparison of Amplifier Classes

This set of Analog Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Comparison of Amplifier Classes”.

1. Which of the following amplifier class have the highest linearity and lowest distortion?
a) Class A
b) Class B
c) Class C
d) Class B push-pull
View Answer

Answer: a
Explanation: Class A amplifier has the highest linearity and the lowest distortion. The amplifying element is always conducting and close to the linear portion of its transconductance curve. The point where the device is almost off is not at a zero signal point and hence its distortions compared to other classes are less.

2. Which of the following letter is not used to represent a class?
a) D
b) E
c) C
d) K
View Answer

Answer: d
Explanation: There is no amplifier called Class K. There are only A, B, C, D, E/F, G, H, S.

3. Which of the following letter is not used to represent a class?
a) I
b) H
c) G
d) S
View Answer

Answer: a
Explanation: There is no amplifier called Class I. There are only A, B, C, D, E/F, G, H, S.
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4. Which of the following class has the poorest linearity
a) Class A
b) Class B
c) Class C
d) Class AB
View Answer

Answer: c
Explanation: Class C amplifiers have high efficiency but have the poorest linearity since they only take less than 180° oscillations. They are suitable for amplifying constant envelope signals.

5. Which of the following amplifier cannot be used for audio frequency amplification?
a) Class A
b) Class C
c) Class AB
d) Class B push-pull
View Answer

Answer: b
Explanation: Class C amplifier cannot be used for audio frequency amplifiers because of its high distortion.
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6. Which of the following amplifier is less efficient than others?
a) Class C
b) Class B
c) Class A
d) Class AB
View Answer

Answer: c
Explanation: Class A amplifiers are the least efficient of all. A maximum of 25% theoretical efficiency is obtainable, 50% for when using transformer or with induced coupling. This wastes power, as well as increases the cost and requires higher rated output devices.

7. Which of the following amplifier is designed to operate in digital pulses?
a) Class D
b) Class C
c) Class AB
d) Class B
View Answer

Answer: a
Explanation: Class D amplifiers use a form of PWM to control the output devices. Conduction angle varies with the pulse width and doesn’t depend on the input directly. The analog signal is converted into a stream of pulses representing the signal using a modulation technique.
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8. Which of the following class have a theoretical efficiency of 50%?
a) Class A
b) Class C
c) Class AB
d) Class D
View Answer

Answer: a
Explanation: Class A amplifier has a theoretical efficiency of 50%. 50% of the energy supplied is a waste.

9. Which of the following class have a theoretical efficiency of 78.5%?
a) Class A
b) Class D
c) Class C
d) Class B
View Answer

Answer: d
Explanation: Class B amplifier has a theoretical efficiency of 78.5% which higher than Class A while Class D theoretically have efficiency of 100%.
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10. Which of the following amplifier is most suited for making tuning circuits?
a) Class A
b) Class B
c) Class C
d) Class D
View Answer

Answer: c
Explanation: Class C is the most suitable amplifier type for tuning circuit and radio frequency amplification. It employs filtering and hence the final signal is completely acceptable. Class C amplifiers are quite efficient than other types.

Sanfoundry Global Education & Learning Series – Analog Circuits.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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