Analog Electronics - Section 1

An amplifier with loop gain Aβ will be more stable for value of Aβ as A. 0.95 B. 0.7 C. 1.2 D. 1.5

B A feedback amplifier is stable if loop gain is less than unity. More less, more stable, hence β will be more stable.

Negative feedback reduces noise originating at the amplifier input. A. True B. False

B It has no effect on noise originating at amplifier input.

An exponential amplifier has diode in feedback path. A. True B. False

B It has resistance in feedback path.

DC amplifiers have a tendency to be unstable. A. True B. False

A Due to drift.

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 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

C

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)

C

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

A Since the characteristics is non-linear, graphical analysis is needed.

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

A

The self bias provides A. stable Q point B. large voltage gain C. high input impedance D. high base current

A

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 Input is applied to base with emitter grounded. The input impedance is the ratio of ac base voltage to ac base current.

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)

A Quiescent-operation means operation when ac signal is not applied.

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)

A Resistor reduces surge current.

A forward voltage of 9 V is applied to a diode in series with a 1 kΩ 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

B

An amplifier has a large ac input signal. The clipping occurs on both the peaks. The output voltage will be nearly a A. sine wave B. square wave C. triangular wave D. (a) or (c)

B

A half wave diode rectifier has a capacitance input filter. If input voltage is Vm sin ωt, PIV is A. Vm B. 2 Vm C. 3 Vm D. 4 Vm

B Because capacitor charge is retained.

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

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

Which of the following oscillators is suitable for frequencies in the range of mega hertz? A. RC phase shift B. Wien bridge C. Hartley D. Both (a) and (c)

C Only LC oscillators are suitable for MHz range.

Which power amplifier can deliver maximum load power? A. Class A B. Class AB C. Class B D. Class C

D

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

D All voltages and currents have reverse polarity.

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. 0 C. more than 90° but less than 180° D. more than 180° but less than 270°

D It is 180° for purely resistive load and between 180° and 270° for R-L load