Question 1

In a BJT circuit a pnp transistor is replaced by npn transistor. To analyse the new circuit

Accepted Answer

All voltages and currents have reverse polarity.

Question 2

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

Accepted Answer

When a sinusoidal voltage is clipped on both sides it resembles a square wave.

Question 3

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

Accepted Answer

As we know, Gain with feedback A = - 1000, β = -0.1 .

Question 4

In the op-amp circuit of figure, V0 =

Accepted Answer

.

Question 5

To protect the diodes in a rectifier and capacitor input filter circuit it is necessary to use

Accepted Answer

Resistor reduces surge current.

Question 6

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

Accepted Answer

D1 will conduct and the output voltage will be about 7 V. Therefore D2 will be reverse biased and will not conduct.

Question 7

In figure ID = 4 mA. Then VS =

Accepted Answer

VS = ISRS = 4 x 10-3 x 1.1 x 103 = 4.4 V.

Question 8

A half wave diode rectifier has a capacitance input filter. If input voltage is Vm sin ωt, PIV is

Accepted Answer

Because capacitor charge is retained.

Question 9

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

Accepted Answer

Efficiency of full wave rectifier with centre tapped transformer is slightly higher than that of bridge rectifier.

Question 10

The transistor of following figure in Si diode with a base current of 40 μA and ICBO = 0, if VBB = 6V, RE = 2 kΩ and β = 90, IBQ = 20 μA then RB =

Accepted Answer

.

Question 11

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

Accepted Answer

Question 12

For a system to work, as oscillator the total phase shift of the loop gain must be equal to

Accepted Answer

Gain of system with + ve feedback = for oscillation but V0 ≠ 0 so, that 1 - AB = 0 ⟹ AB = 1 ∠0° or 360°.

Question 13

The input impedance of op-amp circuit of figure is

Accepted Answer

Due to the presence of virtual ground at input, the resistance in the series path of input of inverting amplifier is input impedance.

Question 14

An RC coupled amplifier has an open loop gain of 200 and a lower cutoff frequency of 50 Hz. If negative feedback with β = 0.1 is used, the lower cut off frequency will be

Accepted Answer

New lower cutoff frequency = .

Question 15

For a base current of 10 μA, what is the value of collector current in common emitter if βdc = 100

Accepted Answer

IC = 10 x 100 μA = 1 mA.

Question 16

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

Accepted Answer

There is 180° phase difference between input and output.

Question 17

Maximum efficiency of class B power amplifier is 50%.

Accepted Answer

Maximum efficiency for class B-operation can be 78.5% .

Question 18

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

Accepted Answer

.

Question 19

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

Accepted Answer

Question 20

In figure what is the base current if VBE = 0.7 V

Accepted Answer

.

Analog Electronics Questions