# Electronic Devices and Circuits Questions and Answers – Class D Amplifiers

This set of Electronic Devices and Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Class D Amplifiers”.

1. Why a class D amplifier is called as switching amplifier?
a) Because it consists of a transistor
b) Because of high power
c) Because of less noise effect
d) Because of binary switch

Explanation: A class D amplifier or switching amplifier is an electronic amplifier where all power devices are operated as binary switches.

2. For an ideal class D amplifier, what time is required in transitioning between states?
a) 0
b) 10
c) 100
d) Infinite

Explanation: For an Ideal class D amplifier, zero time is spent between transitioning from on to off or vice versa.

3. Which of the following is an example for the application of class D amplifier?
a) Switch
b) Torch
c) Pulse generator
d) Bulb

Explanation: The output stages of class D amplifier are used as pulse generator, because of its switching ability.

4. Which of the following is true about class D amplifier?
a) Its efficiency is very less
b) It can be made to work as bulb
c) It is big in size
d) It operates on lesser frequently

Explanation: class D amplifier work by generating a square wave of which the low frequency portions of the spectrum is essentially the wanted output signal.

5. Efficiency of class D amplifier____________
a) 100%
b) 59%
c) 75%
d) 60%

Explanation: Theoretically the efficiency of the class D power amplifier is 100% because of its switching ability.
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6. MOSFET class D amplifier is more advantageous than BJT class D amplifier.
a) True
b) False

Explanation: MOSFET is smaller and is controlled by voltage, hence it is more advantageous compared to BJT.

7. Which of the following is true about MOSFET class D amplifier?
a) It has infinite gain
b) It is less stable
d) It dissipates less heat

Explanation: When MOSFET is off, no current flows and hence no power dissipation occurs.

8. Why the cost of MOSFET based power amplifier is less?
a) High impedance
b) Low capacitance
c) Low power dissipation
d) Lesser in size

Explanation: Since power dissipation in MOSFET is less, this results in smaller heat sinks and thus the cost of the amplifier will be reduced.

9. What is the conduction angle of class D amplifier?
a) 180
b) 270
c) 0
d) 90

Explanation: The conduction angle of class D amplifier is 0 because of its switching ability, it turns on and off non linearly.

10. Why filters are required in class D amplifier?
a) Output is completely dependent on the lower frequency spectrum
b) To increase the complexity
c) To obtain only lower frequency
d) To nullify noise

Explanation: Output is completely dependent on the lower frequency spectrum of the output signal and hence to properly obtain lower frequency components, filters are required.

Sanfoundry Global Education & Learning Series – Electronic Devices and Circuits.

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