BJT Amplifiers and Oscillators MCQs

Question 1

A class-B amplifier has high theoretical efficiency (78.5%) because

Accepted Answer

its quiescent current is low

Answer

it is biased well below cut-off

Answer

it is biased almost to saturation

Answer

it output is an exact replica of its input

Question 2

Which of the following is the main reason for the variation of amplifier gain with frequency?

Accepted Answer

The presence of capacitances, both external and internal

Answer

The Miller effect

Answer

The logarithmic increase in the output power

Answer

Due to interstage transformers

Question 3

Load impedance must match amplifier impedance in order that

Accepted Answer

maximum power is transferred to the load

Answer

signal-to-noise ratio is maximised

Answer

efficiency may be held at a high level

Answer

minimum power is transferred to the load

Question 4

In amplifiers coupling produces minimum interference with frequency response.

Accepted Answer

direct

Answer

transformer

Answer

RC

Answer

impedance

Question 5

A class-C amplifier is used as a

Accepted Answer

R.F. carrier amplifier

Answer

differential amplifier

Answer

audio amplifier

Answer

D.C. amplifier

Question 6

Negative feedback reduces distortion in an amplifier only when

Accepted Answer

it is generated within it

Answer

it exceeds a certain safe level

Answer

it comes as a part of input signal

Answer

it is part of its output

Question 7

In a voltage shunt feedback, the input impedance is

Accepted Answer

decreased

Answer

increased

Answer

remains unchanged amplifier has the highest input impedance

Answer

none of the above

Question 8

Which of the following statements in incorrect?

Accepted Answer

Emitter follower is the same as a common base amplifier circuit

Answer

Negative feedback' in an amplifier increases the stability of its voltage gain

Answer

By introducing negative feedback the upper cut-off frequency of an amplifier is increased

Answer

None of the above

Question 9

The gain of RF amplifier with a tuned LC circuit for the collector is maximum at the resonant frequency because of

Accepted Answer

parallel resonance

Answer

series resonance

Answer

highter emitter resistance

Answer

low Q