IGNOU BPHET-143 December 2022 Previous Year Question Paper

Q1.Attempt any five parts: 5x2=10

(a) Distinguish between the processes causing drift and diffusion by which transport of charge carriers occurs in semiconductor.

(b) Draw the circuit symbol of n-p-n bipolar junction transistor. State its emitter-base and collector-base junction biasing for normal operation as an amplifier.

(c) Convert binary number 1110-10, into its decimal equivalent.

(d) Write down the truth table for the Boolean expression (C + D) C.

(e) Write down the units for the following h-parameters of the transistor :

(i) hy (hp)

(ii) hy, (hy)

(f) State the PIV of the diodes used in a full wave rectifier

(i) when used with centre tapped transformer, and

(ii) when used in bridge configuration.

(g) Write down the values of the following characteristics for an ideal Op-amp :

(i) Input offset voltage

(ii) CMRR

(iii) Output resistance

(iv) Slew rate BPHET-143 2

(h) Why should the trigger pulse used in the monostable mode of IC 555 be very narrow ?

Q2.Attempt any éwo parts : 2x5=10

(a) With the help of an energy band diagram, explain the working of an LED. In which region of I-V characteristics do the LEDs operate ? 441

(b) Explain the Common Base (CB), Common Emitter (CE) and Common Collector (CC) configurations of an n-p-n transistor with the help of appropriate circuit diagrams. 5

(c) Calculate the base voltage, collector voltage and collector to emitter voltage (Vo,); collector and emitter currents for the universal bias. It is given that R, = 40 kQ, R, = 5 kO, Rg = 5 kQ, Veg = 15 V, Rg = 1 kQ. Take Vpp = 0:4 V for the given transistor. Hence, locate its Q-point.

Q3.Attempt any fwo parts : 2x5=10

(a) Draw the circuit of a 2-input NAND gate realised using p-n junction diodes and a transistor. Write its truth table and draw its symbol. 34+1+1

(b) Obtain the MSP expression for the following Boolean equation and draw _ the corresponding simplified logic circuit : Y= AC +(A+C)B 342

(c) With the help of an appropriate circuit diagram, explain the operation of 2’s complement Binary Adder-Subtractor for subtracting binary number 1001, from

Q5.Attempt any two parts : 2x5=10

(a) Explain the classification of amplifiers on the basis of biasing using the diagram of output characteristics with operating point. 5 BPHET-143 4

(b) Draw the circuit diagram of phase-shift oscillator and explain how positive feedback is achieved in this circuit. 5

(c) Design a series pass voltage regulator to obtain 12 V dc output with maximum load current of 50 mA. Consider the nominal input voltage to be 18 V; Vpp = 0-6 V and B = 50 for the series pass transistor.

Q6.Attempt any two parts: 2x5=10

(a) Design an amplifier using Op-amp IC 741C with V; = 0:3 V, for gain of +12 and I, of 0-1mA. 5

(b) Explain the dual trace method of phase difference measurement using a CRO. If ona CRO display, one complete cycle of a wave is 5 cm long on the horizontal scale and if the difference between the maxima of two waves is 0-5 cm, calculate the phase difference. 342

(c) Design and draw the circuit of a monostable multivibrator using IC 555 to give a 50 ms long duration pulse when trigger input is applied. 342 BPHET-143 6 @ hy, (hp

(i) hy, (hy)

(a) wi am fecal A yan cals a PIV fafa BPHET-143 8 Ro = 5 kQ, Vog = 15 V, Ry = 1 KO. दिए गए gifsent & fez V,, = 0-4 V offre | arava, Y= AC +(A+C)B