Question 1

(a) What is an oscillator? How it is differ from an amplifier?

Accepted Answer

An oscillator is a circuit that generates a continuous, periodic waveform without any external AC input, unlike an amplifier which requires an input signal and only magnifies it.

Question 2

(b) Describe Transition and Diffusion capacitance in PN junction diode.

Accepted Answer

Transition capacitance arises due to the depletion layer charge in a reverse-biased PN junction, while diffusion capacitance is due to minority carrier injection under forward bias.

Question 3

(c) Write at least four major differences between BJT and FET.

Accepted Answer

BJT is a current-controlled, bipolar device using minority carriers, while FET is a voltage-controlled, unipolar device using majority carriers, with differences in input impedance, noise, and fabrication.

Question 4

(d) Define voltage follower and slew rate with the help of Operational Amplif…

Accepted Answer

A voltage follower is a unity-gain buffer Op-Amp configuration (Av = +1) with very high input impedance, and slew rate defines the maximum rate of change of output voltage in volts per microsecond.

Question 5

(e) Discuss how does the circuit of Clap oscillator is different from that of…

Accepted Answer

The Clapp oscillator is a modified Colpitts oscillator with an additional series capacitor C3 in the tank circuit inductor branch, giving better frequency stability.

Question 6

(f) Why FET is called as â€œvoltage operated deviceâ€?

Accepted Answer

FET is called a voltage-operated device because its output drain current is controlled entirely by the input gate-source voltage VGS, and the gate draws virtually no current.

Question 7

(g) Which MOSFET is called as Normally ON MOSFET and NORMALLY OFF MOSFET? Why?

Accepted Answer

Depletion-type MOSFET is called Normally ON because it conducts at VGS = 0, while Enhancement-type MOSFET is called Normally OFF because it requires a threshold voltage to start conduction.

Question 8

(A) Estimate dc emitter current in each transistor of differential amplifier …

Accepted Answer

In a balanced differential amplifier, the DC emitter current in each transistor is set by the tail current source, collector voltages are calculated using KVL, and Vout (differential output) is zero for zero differential input.

Question 9

(B) A Colpitt's oscillator is designed with C1= 110 Pf and C2=7500 Pf. The in…

Accepted Answer

Using the Colpitts oscillation frequency formula, the inductance range is calculated for the given capacitors (C1=110pF, C2=7500pF) and frequency range (750kHz to 2050kHz).

Question 10

(A) Determine Vo and sketch output waveform of each circuit for given in fig.…

Accepted Answer

Clipper circuits clip portions of the input waveform above or below a reference level, while clamper circuits shift the entire waveform up or down by adding a DC component.

Question 11

(B) For the circuit shown in fig. 4, find:
(i) output voltage
(ii) voltage dr…

Accepted Answer

For a zener voltage regulator circuit, the output voltage equals the zener breakdown voltage, and the zener current is found by subtracting the load current from the series resistor current.

Question 12

(A) Derive the expression for closed loop Inverting Amplifier, Non inverting …

Accepted Answer

Op-Amp inverting amplifier gives Av = -Rf/R1; non-inverting gives Av = 1+Rf/R1; integrator gives Vout = -(1/RC)âˆ«Vin dt; and differentiator gives Vout = -RC(dVin/dt).

Question 13

(B) For fig. 5 find output voltage of the op-amp.
Given R1 = 5 K\Omega, R2 = …

Accepted Answer

For a difference amplifier with R1=R3 and R2=R4, the output voltage equals (R2/R1) Ã— (V2 - V1); for the given values Vout = 2(V2 - V1).

Question 14

(A) For the circuit shown in fig 6, the transistor parameters are \beta = 100…

Accepted Answer

For a CE amplifier with Î²=100, ICQ=0.25mA, VCEQ=3V, the transconductance gm=ICQ/VT, the voltage gain is Av=-gmÃ—RC, and the input resistance seen by the source includes biasing resistors and rÏ€.

Question 15

(B) For fig. 7 Calculate the quiescent points (ICQ and VCEQ) and also determi…

Accepted Answer

For the voltage divider bias circuit with Î²=100, VCC=16V, the Q-point is found to be ICQâ‰ˆ1.84mA and VCEQâ‰ˆ5.15V.

Question 16

(A) What are the main constructional differences between a MOSFET and a BJT? …

Accepted Answer

MOSFET uses a metal-oxide-semiconductor gate insulated by SiO2 (unlike BJT's p-n junction base), conducts via field-induced channel with majority carriers only, and exists in depletion and enhancement types.

Question 17

(B) Compare the common source, common drain & common gate amplifiers with its…

Accepted Answer

Common Source (CS) gives high voltage gain with phase inversion and moderate impedance; Common Drain (CD) or Source Follower gives unity gain with high Rin and low Rout; Common Gate (CG) gives high gain with low Rin and no phase inversion.

Question 18

Describe the working principle of NPN Transistor as an amplifier. Draw and ex…

Accepted Answer

An NPN transistor amplifies signals by operating in the active region where a small base current controls a large collector current; the CE configuration shows characteristic input (IB vs VBE) and output (IC vs VCE) curves.

Question 19

Draw the neat diagram of full wave bridge rectifier circuit and derive the av…

Accepted Answer

A full-wave bridge rectifier uses four diodes to conduct on both half-cycles of AC, giving DC average value Vdc = 2Vm/Ï€, efficiency Î· = 81.2%, and PIV = Vm.

Question 20

Draw and explain the construction and working principle of N- Channel JFET. D…

Accepted Answer

N-Channel JFET uses a reverse-biased gate to control channel width and drain current via depletion; pinch-off voltage VP is the VGS at which the channel is fully depleted and ID becomes zero.

Question 21

What is cascading or multistage amplifier? Explain the need for cascading of …

Accepted Answer

Cascading amplifiers connects output of one stage to input of the next to achieve higher overall gain; however, the cascaded bandwidth is narrower than that of a single stage.

Question 22

Write the short note on -
(i) Summing amplifier
(ii) Zero crossing detector
(…

Accepted Answer

Summing amplifier adds multiple weighted inputs; zero crossing detector identifies when a signal crosses zero; square wave generator produces square waves; and peak detector captures the peak amplitude of a signal.

Analog Electronics