Deck 4: Transistor Amplifier

Question 1

If the load resistance of a C.E. stage increases by a factor of 2, what happens to the high frequency response?

A)the 3 db roll off occurs faster
B)the 3 db roll off occurs later
C)the input pole shifts towards origin
D)the input pole becomes infinite

Answer 1

the 3 db roll off occurs faster

Question 2

During high frequency applications of a B.J.T., which of the following three stages do not get affected by Miller's approximation?

A)c.e.
B)c.b.
C)c.c.
D)follower

Answer 2

c.b.

Question 3

Ignoring early effect, if C1 is the total capacitance tied to the emitter, what is the input pole of a simple C.B. stage?

A)1/gm * c1
B)2/gm * c1
C)gm * c1
D)gm * 2c1

Answer 3

1/gm * c1

Question 4

In a simple follower stage, C2 is a parasitic capacitance arising due to the depletion region between the collector and the substrate. What is the value of C2?

A)0
B)infinite
C)ccs
D)2*ccs

Question 5

For a cascode stage, with input applied to the C.B. stage, the input capacitance gets multiplied by a factor of          

A)0
B)1
C)3
D)2

Question 6

If the B.J.T. is used as a follower, which capacitor experiences Miller multiplication?

A)c?
B)cµ
C)ccs
D)cb

Question 7

If 1/h12 = 4, for a C.E. stage- what is the value of the base to collector capacitance, after Miller multiplication, at the input side?

A)4cµ
B)5cµ
C)6cµ
D)1.1cµ

Question 8

The transconductance of a B.J.T.is 5mS (gm) while a 2K? (Rl) load resistance is connected to the C.E. stage. Neglecting Early effect, what is the Miller multiplication factor for the input side?

A)21
B)11
C)20
D)0

Question 9

Which of these are incorrect about Darlington amplifier?

A)it has a high input resistance
B)the output resistance is low
C)it has a unity voltage gain
D)it is a current buffer

Question 10

In a Darlington pair, the overall ?=15000.?1=100. Calculate the collector current for Q2 given base current for Q1 is 20 ?A.

A)300 ma
B)298 ma
C)2 ma
D)200ma

Question 11

What is the need for bootstrap biasing?

A)to prevent a decrease in the gain of network
B)to prevent an increase in the input resistance due to the biasing network
C)to prevent a decrease in the input resistance due to the presence of multiple bjt amplifiers
D)to prevent a decrease in the input resistance due to the biasing network

Question 12

Consider a Darlington amplifier. In the self bias network, the biasing resistances are 220k? and 400 k?. What can be the correct value of input resistance if hfe=50 and emitter resistance = 10k?.

A)141 k?
B)15 m?
C)20 m?
D)200 k?

Question 13

What is a cascode amplifier?

A)a cascade of two ce amplifiers
B)a cascade of two cb amplifiers
C)a cascade of ce and cb amplifiers
D)a cascade of cb and cc amplifiers

Question 14

1, ?2 = 1.5 what is the transconductance of the entire network?

A)80 m?-1
B)75 m?-1
C)33 m?-1
D)55 m?-1

Question 15

In the given circuit, hfe = 50 and hie = 1000?, find overall input and output resistance.

A)ri=956?, ro=1.6 k?
B)ri=956 k?, ro=2 k?
C)ri=956 ?, ro=2 k?
D)ri=900?, ro=10 k?

Question 16

Obtain the collector voltage, for collector resistor (RC) =5.6k?, IE=1.664mA and VCC=10v for single input unbalanced output differential amplifier

A)0.987v
B)0.682v
C)0.555v
D)none of the mentioned

Question 17

For the difference amplifier which of the following is true?

A)it responds to the difference between the two signals and rejects the signal that are common to both the signal
B)it responds to the signal that are common to the two inputs only
C)it has a low value of input resistance
D)the efficacy of the amplifier is measured by the degree of its differential signal to the preference of the common mode signal

Question 18

The problem with the single operational difference amplifier is its

A)high input resistance
B)low input resistance
C)low output resistance
D)none of the mentioned