18ELN14/24
Visvesvaraya Technological University, Belagavi
MODEL QUESTION PAPER
1st 2nd Semester, B.E (CBCS)
Course: 18ELN14/24- Basic Electronics Set no. 3
Note: Answer five full questions selecting any one full question from each module.
Missing data may be suitably assumed
Time: 3 Hrs Max. Marks: 100
MODULE 1
1 a Explain the forward and reverse bias condition for a pn junction diode with
neat diagram.
08M
b A half wave rectifier is fed from a supply of 230 50 Hz with step down
transformer of ratio 3:1. Resistive load connected is 10 KΩ. The diode forwardΩ. The diode forward
resistance is 75Ω and transformer secondary is 10 Ω. Calculate the DC load
current, DC load voltage, efficiency and ripple factor.
06M
c Write a short note on the following:
Photo diode Light emitting diode
06M
OR
2 a With neat circuit diagram and wave forms explain the working of a centre
tapped full wave rectifier.
08M
b A Zener diode has a breakdown voltage of 10V. It is supplied from a voltage
source varying between 20-40V in series with a resistance of 820Ω. Using an
ideal Zener model, obtain the minimum and maximum Zener currents
06M
c Explain the features of LM7805 fixed regulator. 06M
MODULE 2
3 a Explain the construction and operation of a p-channel JFET 08M
b With neat diagram explain the operation of a CMOS inverter. 06M
c With neat diagram explain the VI characteristics of an SCR. 06M
OR
4 a Explain the characteristics of an n-channel JEFT. 06M
b With neat diagram, explain the characteristics of a enhancement type
MOSFET.
08M
c With neat diagram explain the two transistor model of an SCR. 06M
MODULE 3
5 a Explain the following with respect to op-amp
Input Impedance output impedance Slew rate CMRR virtual
ground
10M
b Derive an expression for the output voltage of an inverting amplifier. 06M
c The input to the basic differentiator circuit is a sinusoidal voltage of peak
value of 10mV and frequency 1.5KΩ. The diode forwardHz. Find the output if, Rf=100KΩ. The diode forwardΩ and
C1=1μF.F.
04M
OR
6 a Derive an expression for the output voltage of an op-amp integrator. 06M
b Derive an expression for the output voltage of an inverting summer. 06M
c A non-inverting amplifier circuit has an input resistance of 10KΩ. The diode forwardΩ and
feedback resistance 60KΩ. The diode forwardΩ with load resistance of 47KΩ. The diode forwardΩ. Draw the circuit.
Calculate the output voltage, voltage gain, load current when the input voltage
is 1.5V.
08M
MODULE 4
7 a Explain how the transistor can be used as a switch and as an amplifier. 10M
b
An amplifier has a high frequency response described byA= A 0
jωω/ω2).
Where in A0=1000, ω2=104 rad/s. Find the feedback factor which will raise the
upper corner frequency ω2 to 105 Hz. What is the corresponding gain of the
amplifier? Find also the gain bandwidth product in this case.
04M
c With a neat circuit diagram, explain the working of RC phase shift oscillator. 06M
OR
8 a List the advantages of negative feedback in an amplifier. Explain the voltage
series feedback amplifier. Show that the gain band width product for a
feedback amplifier is constant.
10M
b The frequency sensitivity arms of the Wein bridge oscillator uses
C1=C2=0.01μF.F and R1=10KΩ. The diode forwardΩ while R2 is kept variable. The frequency is to be
varied from 10KΩ. The diode forwardHz to 50 KΩ. The diode forwardHz by varying R2. Find the minimum and
maximum values of R2.
04M
c With a neat diagram explain the Astable operation of IC 555 timer. 06M
MODULE 5
9 a Simplify the following Boolean expressions
Y=A ´B AB
AC+BD+CD

Y=´A
´B
´C
´D
+´A
´B
´C
A ´B
´C
´D
A´B
´C
D
08M
b With a neat circuit diagram and truth table, explain the working of a JKΩ. The diode forward flip
flop.
06M
c With a neat diagram, explain the working of a communication system. 06M
OR
10 a Simplify and realize the following using NAND gates only
ABC+´A BC+ AB+D
Y=A ´B
´C
+´A
´B
´C
+´A
´B
+´A
´C
08M
b With a neat circuit diagram and truth table, explain the full adder circuit. 06M
c With a neat block diagram, explain the operating principle of the GSM system. 06M