IGNOU BPHET-143 June 2025 Previous Year Question Paper

Q1.Attempt any five parts : 5x2=10

(a) Draw the labelled I-V characteristics of a Zener diode. 2

(b) Draw the circuit symbols of an LED and a photodiode. 141

(c) Convert the octal number (516)s into its equivalent binary number. 2

(d) Draw the circuit symbol and write the truth table for a 2-input NAND gate. 141

(e) Classify amplifiers according to frequency. 2

(f) In a Wien bridge oscillator, 10 kQ resistors and 5.0 nF capacitors are used. What is its frequency of oscillations ? 2

(g) Define CMRR and slew rate for an Op- Amp. 141

(h) What will be the effect on the frequency of an astable multivibrator, if the supply voltage to IC 555 is increased by 5 V ? Explain why.

Q2.Attempt any two parts: 2x5=10

(a) Draw a labelled schematic diagram showing the construction of a solar cell. Explain its working. 243

(b) Draw a p-n-p transistor biased for amplifier operation and label the currents that flow in it. Explain its working. 243

(c) The h-parameters for a transistor in CB configuration are : hy, = 20, h,, = 2x10", hy, =-0.99, h,, =0.3us. Calculate Ai and Av. Take the load resistance to be 1kQ.

Q3.Attempt any two parts: 2x5=10

(a) Explain with the help of a circuit diagram how a NOT gate is realised using BJT. What is the combination of NOT and OR gate called ? Write the truth table of the resulting gate for 2 inputs. 3+14+1

(b) Obtain the MSP expression for the following Boolean equation and draw its simplified logic circuit : 3+2 Y=AC+(A+O)B

(c) Draw the circuit of a 2’s complement binary adder and explain its working.

Q4.Attempt any two parts: 2x5=10

(a) Draw the circuit of a class A power amplifier. The quiescent operating collector current of a class A power amplifier is 20 mA. If Vcc is 10 V, calculate the input d.c. power to the circuit. Calculate output a.c. power if the efficiency of the amplifier is 10%. 34141

(b) Explain the working of a phase shift oscillator with the help of its circuit diagram. Write the expression for its frequency of oscillation. 4+1

(c) Draw the circuit diagram of a half-wave rectifier using a transformer, a diode and a load resistor and explain its working. Draw the output waveform if the input waveform is sinusoidal.

Q5.Attempt any two parts: 2x5=10

(a) Draw the circuit diagram of an inverting amplifier using an Op-Amp. Obtain the expression for its gain. 2+3

(b) Explain the functions of five subsystems of a general purpose CRO. 5

(c) Design and draw _ the _ astable multivibrator circuit to produce 40% duty cycle at 10 kHz frequency. 5 hy, = 200, h,, = 2x10", hy, =-0.99, h,, =0.3us | 3+2 Y =AC+(A+O0)B

(1) ufenfita (transformer), Sas AR लोड