IGNOU BPHET-143 December 2024 Previous Year Question Paper

Q1.Attempt any five parts : 5x2=10

(a) Draw the labelled energy band diagram of an intrinsic semiconductor for T>O0 K. 2

(b) Draw the circuit symbols of a Zener diode and a photodiode. 141

(c) Convert the binary number 11000111 into a decimal number. 2

(d) Draw the circuit symbol of a 2-input NOR gate and write its truth table. 141

(e) Distinguish between the biasing of Class A and Class B amplifiers. 2

(f) A transistor phase shift oscillator uses three identical RC sections in the feedback network. The values of the components are R=50kQ and C=0.02 uF. Calculate the frequency of oscillation. 2

(g) Calculate the gain of the amplifier shown below : 2 90 kQ pes kQ Vin tL

(h) What is an astable multivibrator ?

Q2.Attempt any two parts: 2x5=10

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

(b) Draw the labelled drain characteristics of an n-channel JFET for gate-source voltage Vag <0 and explain them. 8+2

(c) Draw the labelled output characteristics of a BJT in CE configuration indicating the active, saturation and cut-off regions. How is the biasing of the base-emitter and collector-emitter junctions done in these three regions ?

Q3.Attempt any two parts: 2x5=10

(a) Explain how a 2-input AND gate is realized using p-n junction diodes. Write the truth table of 2-input AND gate. 4+1

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

(c) Draw the schematic diagram of a 4-bit binary adder used for adding 1011 and

Q4.What is the sum in binary and decimal systems ?

Q5.Attempt any two parts: 2x5=10

(a) An n-p-n transistor is biased using universal biasing for a CE amplifier. If Voc =15V,R, = 20kQ,R, =10kQ, collector current = 10 mA, Vcr = 6 V, Vas = 0.6 V and B=60, calculate the values of the collector resistance Rc and_ emitter resistance Rg. Also determine the output voltage at the collector of the transistor. 5

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

(c) State the function of a filter used in regulated power supply. Explain the action of inductance filter with a full wave rectifier using appropriate waveforms.

Q6.Attempt any two parts: 2x5=10

(a) Explain the working of a non-inverting op- amp comparator as a voltage level detector giving its circuit diagram. For an applied reference voltage of +2 V, draw the output waveform if a sine wave of 5 V amplitude is given at the input. 8+2

(b) Write the basic functions of any five controllers on the front panel of a CRO. 1x5=5

(c) Design an astable multivibrator with 1 kHz frequency and 70% duty cycle. 5 R=50kQ AR C=0.02 pF Zl dem Ft 90 kQ eel 15kQ = Vo Vin fT aif! 342 8+2 करके at fragt aren AND we oa ora Y =CA+BC(B+ A) एक npn gee wr ae adie 10 mA, Ve = 6 V, Vaz = 0.6 V SI 8-60