Network Analysis and Analog Electronics — DU B.Sc. (Prog.) Physical Science courses pertaining to Electronics Previous Year Question Papers

Networks Analysis and Analog Electronics B.Sc. Prog.-(Physics)_NEP: Attempt four questions in all. Answer three questions from rest of the paper. 1. Do any five parts out of the following: (3x5=15) (a) How does a zener diode regulate voltage? Define load and line regulation. (b) How to choose the value of the shunt capacitor filter in a rectifier for a given input signal of frequency 'f'? ( c) What is Early Effect? How does it modify the output characteristics of a BJT? (d) State Barkhausen' s criterion for sustained oscillations. List one use each of positive feedback and negative feedback. (e) If a.= 0.99 and IE= 1 mA for a transistor, what will be the base and collector currents? (f) A voltage source is having an open circuit voltage of 200 V and internal resistance of son. What will be its equivalent current source? 2. (a) Determine the mesh currents 11 and 12 in the following circuit. What is the voltage drop across the 12Q resistance? (6) (b) What are the characteristics of an ideal voltage source and an ideal current source? For an ideal voltage source V = 300 cos 1 00t. Obtain the peak to peak, de and rms values of voltage. ( 4,5) 3 • (a) For a half wave rectifier obtain the expressions for the DC load voltage and the rms value of the load current. The forward resistance of the diode is Rr and the load resistance is Rv (8) (b) A half wave rectifier circuit is supplied from a 230V, 50 Hz supply with a step down transformer ratio of 3: 1 to a resistive load of 1 0kQ. The diode forward resistance is 75Q while transformer secondary resistance is 1 on. Calculate maximum, average and RMS values of current. What is the efficiency of the rectifier? (7) 4. (a) List two advantages of a bridge rectifier over a center tapped full wave rectifier. (4) (b) Convert the given star network into delta network. (5) (c) In an RC phase shift oscillator, if Rl = R2 = R3 is 200 Kfl and Cl and C2 and C3 = 100 PF. Find the frequency of the oscillator. Draw the diagram of the circuit. (6) 5. (a) Plot the output characteristics of a transistor in CB configuration and indicate the various regions of operation on it. (6) (b) In the following circuit, V BE =0. 7V and le= 50 18 . Find IB, le and V CE' Plot the Q point on the de load line for this circuit. (9)