IGNOU BPHET-143 June 2022 Previous Year Question Paper

Q1.Attempt any five parts : 2×5=10

(a) With the help of an appropriate diagram, explain the concept of hole in semiconductor covalent bonding.

(b) Draw the circuit symbol of an n-channel JFET. How is it biased for normal operation ?

(c) Convert octal number (125)8 into its decimal equivalent.

(d) Write down the truth table for the Boolean expression Y =

(e) What is the gain of a multistage amplifier whose individual stage gains are 20, 30 and 50 ?

(f) State the Barkhausen criterion for obtaining sustained oscillations.

(g) State the pin numbers of inputs and outputs of op-amp. IC741C.

(h) Which controls on the CRO front panel will you use to

(i) obtain sharp display line s, and

(ii) select the time base speed ?

Q2.Attempt any two parts :

(a) Explain the formation of the p-n junction and depletion region with the help of a labelled diagr am. Define barrier potential and state its polarity. 3+1+1

(b) Draw the labelled output characteristics of a BJT in CE configuration explaining the features of each region. 2+1+1+1

(c) Explain the universal biasing of an n-p-n transistor in common emitter configuration with the help of an appropriate diagram. How is the Q -point stabilized in this circuit ?

Q3.Attempt any two parts :

(a) Explain how a 2 -input AND gate is realised using p-n junction diodes. Write the truth table of AND gate and draw it s symbol. 3+1+1

(b) Simplify the following Boolean equation and draw the correspo nding simplified logic circuit : 3+2 Y = AB+ AC (C+ B)

(c) With the help of an appropriate circuit diagram, explain the operation of a 4 -bit binary adder for adding the binary numbers 1010 and 1001. 5 [ 4 ]

Q4.Attempt any two parts :

(a) Obtain the expression for the current gain of a CE amplifier in terms of its h- parameters. Consider the load resistance to be Lr . 5

(b) Draw the circuit diagram of a Hartley oscillator. Calculate its frequency of oscillations if the input and output inductors are 0.2 mH each and capacitor is

Q5.01

(c) Design a shunt regulator using Zener diode to provide 10 V d .c. voltage for variable load of 100 to 500 . The unregulated input voltage is 12 V and consider the minimum Zener operational current to be 5 mA.

Q6.Attempt any two parts :

(a) Explain the following parameters of an op - amp. and state their ideal values : 3+2

(i) CMRR

(ii) Input offset voltage

(b) Draw the circuit of basic integrator using an op -amp. and obtain the expression for its output voltage. 2+3

(c) Design an astable multivibrator using IC555 to obtain the 1 kHz rectangular wave with 70% duty cycle. 5 2022 -143 JFET C + D CRO

(ii) p-n 3+1+1 BJT 2+1+1+1 3+2 p-n AND AND 3+1+1 3+2 Y = AB + AC C + B [ 10 ]