IGNOU BPHET-143 December 2023 Previous Year Question Paper

Q1.Attempt any five parts : 5×2=10

(a) Distinguish between solar cell and photodiode.

(b) Why is it necessary to nulli fy the output offset voltage in op-amp 741 ?

(c) Write any four characteristics of an ideal operational amplifier.

(d) What is aquadag coating in a CRO ? What is its function ?

(e) For a semiconductor material of a light emitting di ode the energy gap is 1.37 eV.

Q2.What is the wavelength of the emitted light ?

(f) Draw the circuit diagram of centre -tap full wave rectifier.

(g) Express hexadecimal number 8AE in its decimal equivalent.

(h) Write any four advantages of negative feedback in an amplifier circuit.

Q3.Attempt any two parts :

(a) With a suitable diagram , explain the formation of depletion layer in p-n junction. What is the effect of increasing the reverse voltage on the depletion region ? 4+1

(b) Draw and discuss the input and output characteristics of an n-p-n transistor in CE configuration. 5

(c) An n-p-n transistor with  = 50 is used in CE circuit with VCC = 10 V, RC = 2 k. The bias is obtained by connecting a 100 k  resistance from colle ctor to base as shown in the figure. Assume V BE = 0.7 V. Determine the Q-point for the circuit.

Q4.Attempt any two parts :

(a) Prove the following Boolean identities using the laws of Boolean Algebra :

(ii) ABC + ABC + ABC + ABC = AB + BC + AC

(b) How can a 2 input AND gate be realised using p-n junction di odes ? Draw the electronic circuit. Write its truth table and symbol. 3+1+1

(c) Draw the binary adder circuit for adding 4 - bit binary numbers 1000 and 1010. Indicate the final sum and carry output.

Q5.Attempt any two parts :

(a) Draw and explain h-parameter equivalent circuit for a BJT. What are the electrical units of the four h-parameters ? 3+2

(b) Explain with a neat di agram how Zener diode can be used for voltage regulati on. Define the terms source regulation and load regulation. 3+2

(c) Draw the circuit diagram o f an inventing amplifier using a n op-amp 741C to obtain closed loop gain of – 10. For V i = 1 V and Io = 1.1 mA, calculate IL. 3+2 [ 5 ]

Q6.Attempt any two parts :

(a) Design a monostable multivibrator using IC 555 to obtain a pulse width of 10 ms and draw its circuit diagram. 2+3

(b) With the help of a diagram, explain the working of a horizontal deflection system in a CRO. Describe how the frequency phase of sinusoidal waves can be measured using a CRO. 3+2

(c) Draw the pin out diagram of op-amp 741C. What is common mode rejection ratio (CMRR) of an op-amp ? 2+3 2023 -143 OP-amp 741 CRO (LED)