# Linear Integrated Circuit Questions and Answers – Power Amplifiers

This set of Linear Integrated Circuit Multiple Choice Questions & Answers (MCQs) focuses on “Power Amplifiers”.

1. Output current in general purpose op-amp can be increased using
a) Power comparator
b) Power amplifier
c) Power resistor
d) Power booster

Explanation: A simple method of increasing output current of a general purpose op-amp is to connect a power booster in series with the op-amp.

2. Which type of power transistor is chosen for a discrete power booster?
a) Collector follower stage
b) Emitter follower stage
c) Base follower stage
d) None of the mentioned

Explanation: A discrete power booster is formed by an emitter follower stage using a power transistor. Because of unity gain, the emitter follower helps to retain the voltage gain characteristics of the general purpose op-amp.

3. What is the power dissipation of power transistor?
a) ≅ 0.5W
b) ≤ 0.5W
c) > 0.5W
d) ≠ 0.5W

Explanation: Transistors with power dissipation larger than 1/2 (0.5)W are called power transistors.

4. Burr-Brown 3553 power amplifier is suited for
a) Line driving applications
b) Power supply requirement
d) High frequency application

Explanation: Burr-Brown 3553 power amplifier is suited for line driving applications in which fast pulses or wideband signals are involved.

5. Find the IC that can be used for short circuit proof protection?
a) All of the mentioned
b) IC LM384
c) ICL8063
d) ICLM380

Explanation: The intersil ICL8063 monolithic power transistor driver and amplifier has a built-in safe area protection and short-circuit proof protection.
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6. Which among the following is ideal for consumer applications?
a) NE5018
b) LM380
c) MC1408
d) SE5018

Explanation: LM380 is a power audio amplifier designed to deliver a minimum of 2.5w to an 8Ω load and hence is ideal for consumer applications.

7. Bridge power audio amplifier can deliver power upto
a) Twice as much as output of single LM380 amplifier
b) Thrice as much as output of single LM380 amplifier
c) Four times as much as output of single LM380 amplifier
d) Half of the output of single LM380 amplifier

Explanation: Two LM380s are used in the bridge configuration.Therefore, it produce a maximum output voltage swing which is equal to twice that of a single LM380 amplifier.

8.

What precautionary measure should be taken if the circuit is used in a RF-sensitive environment?
a) Connect a parallel combination of RC at the output
b) Connect a series combination of Resistors at the output
c) Connect parallel capacitor at the output
d) Connect a series combination of RC at the output

Explanation: When LM380 audio power amplifier is used in an RF-sensitive environment, an RC combination should be added at the output terminal (Pin 8) to eliminate 5 to 10-MHz oscillation.

9. Which amplifier provides twice output swing as that of LM380 amplifier?
a) Hybrid power amplifier
b) Bridge power audio amplifier
c) Monolithic power audio amplifier
d) Dual power amplifier

Explanation: In bridge power audio amplifier, two LM380s are used in bride configuration. Therefore, the maximum output voltage swing will be twice that of a single LM380 amplifier.

10. A LM380 power amplifier is used in a intercom system with amplifier gain = 50 and the transformer turns ratio is given as 35.Find the overall gain of the circuit.
a) 1880
b) 1750
c) 1370
d) 1580

Explanation: Given, N1/N2=35; Gain of amplifier = 50.Therefore, the overall gain of the circuit = 50×35 =1750.

11. Determine the work done by the intercom system depending on the position of the switch

a) Remote speaker act as microphone
b) Master speaker act as microphone
c) Remote and master speaker act as microphone
d) None of the mentioned

Explanation: When the switch of the intercom system is in the listen mode, the remote speaker acts as the microphone.

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