BJT Amplifiers and Oscillators MCQs

Question 1

Four CB stages were cascaded together to get an overall gain of 100. Assuming that cascading is direct, could you have an idea of gal.: per stage.

Accepted Answer

Yes, it will be 100 only

Answer

It is 25

Answer

It is (100)1I4

Answer

It is indeterminate

Question 2

An amplifier comprises of four stages of CE configuration with a voltage?gain of about 30 per stage. Overall gain is approximately

Accepted Answer

8 x 105

Answer

120

Answer

30

Answer

none of these

Question 3

The input impedance of an overall

Accepted Answer

is less than the input impedance of amplifier transistor itself

Answer

is greater than the input impedance of transistor itself

Answer

is equal to the input impedance of transistor itself

Answer

Fig. 4.7

Question 4

The output voltage in a CE amplifier is

Accepted Answer

out of phase with the input by 90?

Answer

in phase with the input

Answer

having a phase difference of 180? with input

Answer

none of these

Question 5

Unlike tansformers, AC amplifiers are capable of both voltage as well as current gains, i.e. output power is greater than the power applied at the input or you can say that energy is being derived from somewhere. Don't you think law of CONSERVATION OF ENERGY is being violated.

Accepted Answer

It is not being violated as the energy is circuits being derived from DC supply used for active devices

Answer

This law is not valid for electronic

Answer

There is no question of the law being violated as no amplifier gives both current and voltage gains

Answer

has nothing to do with the input impedance of transistor

Question 6

Typical value of input impedance of a common?emitter (CE) amplifier stage is

Accepted Answer

50 Ica

Answer

100 CZ

Answer

10 Ma

Answer

1000M"

Question 7

Input and output from a CE amplifier were fed to an oscilloscope to see their was phase relationship. The Lissajous figure

Accepted Answer

a straight line making an obtuse angle with-l-ve X?axis

Answer

an ellipse

Answer

a circle

Answer

a figure?eight pattern

Question 8

Input and output from a CB amplifier when fed to an oscilloscope to see their Phase relationship yielded

Accepted Answer

a straight line lissajous pattern

Answer

an ellipse lissajous pattern

Answer

an oblique ellipse lissajous pattern

Answer

a circle lissajous pattern

Question 9

Current gain of a CE amplifier is 50. Its hfd is approximately

Accepted Answer

50

Answer

25

Answer

100

Answer

none of these