1.

To prevent a DC return between source and load, it is necessary to use

A.

resistor between source and load

B.

inductor between source and load

C.

capacitor between source and load

D.

either (a) or (b)

A.

1/2

B.

1/3

C.

1/6

D.

1/12

Answer: Option B
Explanation:

Answer: Option C
Explanation:
Capacitor offers infinite impedance to DC.
2. For a base current of 10 A, what is the value of collector current in
common emitter if dc = 100
A.

10 A

B.

100 A

C.

1 mA

D.

10 mA

5. A half wave diode circuit using ideal diode has an input voltage 20 sin
t volts. Then average and rms values of output voltage are
A.

B.

Answer: Option C
Explanation:
IC = 10 x 100 A = 1 mA.

C.

3. Which of the following oscillators is suitable for frequencies in the

range of mega hertz?

D.

A.

RC phase shift

B.

Wien bridge

C.

Hartley

D.

Both (a) and (c)

Answer: Option C
Explanation:
Only LC oscillators are suitable for MHz range.
4. If the input to the ideal comparator shown in the figure is a sinusoidal
signal of 8 V (peak to peak) without any DC component, then the
output of the comparator has a duty cycle of

and 10 V
and 10 V

and 5 V
and 5 V

Answer: Option B
Explanation:
and VC = 0.5 x 20 = 10 V.
6. An RC coupled amplifier has an open loop gain of 200 and a lower
cutoff frequency of 50 Hz. If negative feedback with = 0.1 is used,
the lower cut off frequency will be
A.

about 50 Hz

B.

about 5 Hz

C.

about 2.38 Hz

D.

about 70.5 Hz

Answer: Option C
Explanation:

New lower cutoff frequency =

7. In figure v1 = 8 V and v2 = 4 V. Which diode will conduct?

A.

B.

A.

D2 only

B.

D1 only

C.

Both D1 and D2

D.

Neither D1 nor D2

Answer: Option B
Explanation:
D1 will conduct and the output voltage will be about 7 V. Therefore D 2 will
be reverse biased and will not conduct.

C.

D.
Answer: Option B
Explanation:
By using Miller theorem circuit can be redrawn as

8. The load impedance ZL of a CE amplifier has R and L in series. The

phase difference between output and input will be
A.

180

B.

C.

more than 90 but less than 180

D.

more than 180 but less than 270

Answer: Option D
Explanation:
It is 180 for purely resistive load and between 180 and 270 for R-L
load.
9. Gain of the amplifier is 'A'. Then the I/P impedance and O/P impedance
of the closed loop amplifier shown below would be

.
10. If an amplifier with gain of - 1000 and feedback factor = - 0.1 had a
gain change of 20% due to temperature, the change in gain of the
feedback amplifier would be
A.

10%

B.

5%

C.

0.2%

D.

0.01%

Answer: Option C
Explanation:

As we know, Gain with feedback

Explanation:

A = - 1000, = -0.1 .

VC = 20 - 1.98 x 10-3 x 5.4 x 103

11. In figure The minimum and maximum load currents are

13. The input impedance of op-amp circuit of figure is

A.

0 and 60 mA

B.

0 and 120 mA

C.

10 mA and 60 mA

A.

120 k ohm

D.

10 mA and 120 mA

B.

110 k ohm

C.

infinity

D.

10 k ohm

Answer: Option B
Explanation:
When RL = , IL = 0,
When RL = 100 ,

or 120 mA.

12. In figure, VEB = 0.6 V, = 99. Then VC and IC are

9.3 V.

Answer: Option D
Explanation:
Due to the presence of virtual ground at input, the resistance in the series
path of input of inverting amplifier is input impedance.
14. In a BJT circuit a pnp transistor is replaced by npn transistor. To
analyse the new circuit

A.

9.3 V and 1.98 mA respectively

B.

4.6 V and 1.98 mA respectively

C.

9.3 V and 0.02 mA respectively

D.

4.6 V and 0.02 mA respectively

Answer: Option A

A.

all calculations done earlier have to be repeated

B.

replace all calculated voltages by reverse values

C.

replace all calculated currents by reverse values

D.

replace all calculated voltages and currents by reverse values

Answer: Option D
Explanation:
All voltages and currents have reverse polarity.
15. To protect the diodes in a rectifier and capacitor input filter circuit it is
necessary to use

A.

surge resistor

B.

surge inductor

C.

surge capacitor

D.

both (a) and (b)

Answer: Option A
Explanation:
Input is applied to base with emitter grounded. The input impedance is the
ratio of ac base voltage to ac base current.
18. For a system to work, as oscillator the total phase shift of the loop gain
must be equal to

Answer: Option A
Explanation:
Resistor reduces surge current.

A.

90

B.

45

C.

270

D.

360

Answer: Option D
Explanation:

16. The output V0 in figure is

Gain of system with + ve feedback =

but V0 0
so, that 1 - AB = 0
AB = 1 0 or 360.

for oscillation

19. An amplifier has a large ac input signal. The clipping occurs on both
the peaks. The output voltage will be nearly a

A.

-100 V

B.

-100 mV

C.

10 V

D.

10 mV

sine wave

B.

square wave

C.

triangular wave

D.

(a) or (c)

Answer: Option B
Explanation:
When a sinusoidal voltage is clipped on both sides it resembles a square
wave.

Answer: Option B
Explanation:
Input to non-inverting op-amp is -10 x 10-6 x 103 = -10 mV.

Therefore output =

A.

20. The transistor of following figure in Si diode with a base current of 40

A and ICBO = 0, if VBB = 6V, RE = 2 k and = 90, IBQ = 20 A then
RB =

= -100 mV.

17. In a CE amplifier the input impedance is equal to the ratio of

A.

ac base voltage to ac base current

B.

ac base voltage to ac emitter current

C.

ac emitter voltage to ac collector current

D.

ac collector voltage to ac collector current

A.

200 k

B.

265 k

C.

150 k

C.

A is correct R is wrong

D.

100 k

D.

A is wrong R is correct

Answer: Option B
Explanation:

Answer: Option C
Explanation:
There is 180 phase difference between input and output.
.

21. In the amplifier circuit of figure hfe = 100 and hie = 1000 . The
voltage gain of amplifier is about

24. Assertion (A): For large signal variations an amplifier circuit has to be
analysed graphically
Reason (R): The output characteristics of a transistor is nonlinear.
A.

Both A and R are correct and R is correct explanation for A

B.

Both A and R are correct but R is not correct explanation for A

C.

A is correct R is wrong

D.

A is wrong R is correct

Answer: Option A
Explanation:
Since the characteristics is non-linear, graphical analysis is needed.
A.

0.33

B.

0.5

C.

0.66

D.

25. Negative feedback reduces noise originating at the amplifier input.

A.

True

B.

False

Answer: Option B
Explanation:
It has no effect on noise originating at amplifier input.

Answer: Option D
Explanation:

26. Maximum efficiency of class B power amplifier is 50%.

.
22. The efficiency of a full wave rectifier using centre tapped transformer is
twice that in full wave bridge rectifier.
A.

True

B.

False

Answer: Option B
Explanation:
Efficiency of full wave rectifier with centre tapped transformer is slightly
higher than that of bridge rectifier.

A.

True

B.

False

Answer: Option B
Explanation:
Maximum efficiency for class B-operation can be 78.5% .
27. In figure what is the base current if VBE = 0.7 V

23. Assertion (A): CE amplifier is the most widely used BJT amplifier
Reason (R): CE amplifier has zero phase difference between input
and output
A.

Both A and R are correct and R is correct explanation for A

A.

10 mA

B.

Both A and R are correct but R is not correct explanation for A

B.

9.3 mA

C.

10 A

D.

9.3 A

Answer: Option D
Explanation:
.
28. In figure ID = 4 mA. Then VS =

A.

5 mA

B.

5 A

C.

10 mA

D.

10 A

Answer: Option C
Explanation:
Since IB = 100 A, IC = IB = 10 mA.
31. In figure the saturation collector current is
A.

20 V

B.

4.4 V

C.

0.4 V

D.

0.44 V

Answer: Option B
Explanation:
VS = ISRS = 4 x 10-3 x 1.1 x 103 = 4.4 V.
29. The self bias provides
A.

stable Q point

B.

large voltage gain

C.

high input impedance

D.

high base current

nswer: Option A
Explanation:
Stable Q point is the advantage of self bias circuit.
30. In figure what is value of IC if dc = 100. Neglect VBE

A.

B.

C.
D.

none of the above

Answer: Option C

Explanation:

Since IE

IC ,

32. Consider the following statements : A clamper circuit

1. adds or subtracts a dc voltage to a waveform
2. does not change the waveform
3. amplifiers the waveform
Which are correct?
A.

1, 2

B.

1, 3

C.

1, 2, 3

D.

2, 3

Answer: Option A
Explanation:
Clamper does not amplify the waveform. Hence 1 and 2 are correct.
33. In figure v1 = 8 V and v2 = 8 V. Which diode will conduct?

A.

D1 only

B.

D2 only

C.

Both D1 and D2

D.

Neither D1 nor D2

Answer: Option C
Explanation:
Both D1 and D2 are forward biased.
34. A forward voltage of 9 V is applied to a diode in series with a 1 k load
resistor. The voltage across load resistor is zero. It indicates that
A.

diode is short circuited

B.

diode is open circuited

C.

resistor is open circuited

D.

diode is either short circuited or open circuited

Answer: Option B
Explanation:
Since load voltage is zero, the current is zero and diode is open-circuited.
If load was open-circuited, load voltage would be about 9 V.
35. Which power amplifier can deliver maximum load power?
A.

Class A

B.

Class AB

C.

Class B

D.

Class C

Answer: Option D
Explanation:
Since efficiency of class C operation is high, maximum load power is
delivered.
36. A CB amplifier has re = 6 , RL = 600 and = 0.98. The voltage
gain is
A.

100

B.

600 x 0.98

C.

98

D.

Answer: Option C
Explanation:

37. A bridge rectifier circuit has input of 50 Hz frequency. The load

resistance is RL and filter capacitance is C. For good output wave
shape, the time constant RLC should be at least equal to
A.

10 ms

B.

20 ms

C.

50 ms

D.

100 ms

Answer: Option D
Explanation:

Time constant RLC must be about 5 x 20 ms.

38. Si transistor of following figure has = 0.9 and ICE= 0, VEE = 5 V and
VCC = 13 V, then RE will be if IEQ = 1 mA

A.

3 k

B.

4 k

C.

5 k

D.

4.3 k

A.

0.99

B.

1.98

C.

2.0

D.

Answer: Option D
Explanation:

Zi = 25 + 10-6 x 0.99 x 104

25

Answer: Option D
Explanation:

.
41. An exponential amplifier has diode in feedback path.

39. In class C operation of an amplifier circuit, the collector current exists

for

A.

True

B.

False

A.

360 of input wave

Answer: Option B
Explanation:
It has resistance in feedback path.

B.

180 of input wave

42. DC amplifiers have a tendency to be unstable.

C.

more than 180 of input wave

D.

less than 180 of input wave

Answer: Option D
Explanation:
In class C operation output is in the form of short duration pulses.
40. The 'h' parameters of the circuit shown in the figure are hib = 25
, hfb = 0.999 and hob= 10-6 The Voltage gain is

A.

True

B.

False

Answer: Option A
Explanation:
Due to drift.
43. A half wave diode rectifier has a capacitance input filter. If input
voltage is Vm sin t, PIV is
A.

Vm

B.

2 Vm

C.

3 Vm

D.

4 Vm

Answer: Option B

Explanation:
Because capacitor charge is retained.
44. An amplifier with loop gain A will be more stable for value of A as
A.

0.95

B.

0.7

C.

1.2

D.

1.5

Answer: Option B
Explanation:
A feedback amplifier is stable if loop gain is less than unity. More less,
more stable, hence will be more stable.
45. Study the circuit of figure and examine the following statements

A.

0.3

B.

0.4

C.

0.6

D.

none

Answer: Option C
Explanation:
Vs = 10 cos t,
Let I be the current, then P = I2 R
I is the rms current.
Prms =

I2 R

Total power drawn =

I2 = 4

I = 2A.

Vm Im cos

10 x 2 cos = 10 cos
Total power cannot be determine until value of R = 12 is given.
1.
2.
3.
Which

It is an active low pass finer.

It is a second order filter.
The change in gain is 40 dB/decade.
of the above statements are correct?

A.

1, 2 and 3

B.

1 and 2

C.

1 and 3

D.

2 and 3

Answer: Option A
Explanation:
The circuit is a second order active low pass filter for which gain is 40
dB/decade.
46. In a circuit of figure, Vs = 10 cos(t) power drawn by the 2 resistor
is 4 watts. The power factor is

47. The quiescent collector current IC, and collector to emitter voltage
VCE in a CE connection are the values when
A.

ac signal is zero

B.

ac signal is low

C.

ac signal is negative

D.

either (a) or (b)

Answer: Option A
Explanation:
Quiescent-operation means operation when ac signal is not applied.
48. In the op-amp circuit of figure, V0 =

A.

Vi

B.

3 Vi

C.

5 Vi

D.

0.5 Vi

Answer: Option C
Explanation:
.
49. Figure shows the self bias circuit for CE amplifier and its equivalent
circuit. VBB and RBrespectively are

A.

10 V and 4 k ohm

B.

5 V and 4 k ohm

C.

2 V and 4 k ohm

D.

2 V and 10 k ohm

Answer: Option C
Explanation: