BJT Amplifiers and Oscillators MCQs

Question 1

In order to avoid a high noise figure in an amplifier, the volume control should

Accepted Answer

not have large dc current flowing through it

Answer

have a value less than 5 kfl

Answer

have a value greater than 5 K2

Answer

be much less than base resistance

Question 2

For sustaining oscillations, power gain of an amplifier

Accepted Answer

may/be equal to or greater than 1.0

Answer

may be between 0.25 and 0.75

Answer

may be any value from 0.5 upwards

Answer

must be greater than 1.0

Question 3

A high-Q tuned circuit in an amplifier permits it to have high

Accepted Answer

selectivity

Answer

fidelity

Answer

sensitivity

Answer

frequency range

Question 4

Regarding alpha cut-off frequency fa of a transistor, which of the following statement is not true?

Accepted Answer

it is lower than beta cut-off frequency,

Answer

it is the frequency at which cc of the transistor drops to 0.707 of its low frequency value cco

Answer

it is also known as 3-dB frequency

Answer

it is the frequency at which power gain 11 of the transistor is down by 1/2

Question 5

The relationship between fa and frequencies of a transistor is

Accepted Answer

= K(1 ? a) fu

Answer

f?B = K(1 + a) fa

Answer

fcx = K(1 ? cc) fp

Answer

fp = K(1 ? cc) / fa

Question 6

The gain-bandwidth product transistor is given by

Accepted Answer

fT = x

Answer

fT = 130/fp

Answer

fT =130/fa

Answer

fT=I3Oxf

Question 7

A transistor has gain-bandwidth product of 1000 MHz and 130 = 100. The approximate value of its f MHz.

Accepted Answer

1000

Answer

10

Answer

104

Answer

100

Question 8

A transistor has gain-bandwidth product of 1000 MHz and 130 = 100. The approximate value of fp is ___ MHz

Accepted Answer

(g) 10

Answer

800

Answer

500

Answer

none of the above

Question 9

The biggest disadvantage of directcou pled & amplifiers is that

Accepted Answer

Hartley

Answer

they cannot amplify ac voltage

Answer

they do not use capacitors between different stages

Answer

Armstrong