Deemed University 2009 A.M.I.E.T.E Electronics

Q.4 a. Draw the Low Frequency model of a Source Follower Amplifier using FET and derive an expression for its voltage gain. (8)

b. A Transformer-Coupled Class-A Power Amplifier draws a current of 250 mA from a Collector supply of 12.5 V, when no signal is applied to it. Determine
(i) Maximum Output Power
(ii) Maximum Collector Efficiency and
(iii) Power rating of the transistor
If the load connected across the transformer secondary is of two and transformer turn ratio is 5:1, then comment on the Impedance Matching of this amplifier. (8)

Q.5 a. The gain of an amplifier without feedback is 100 whereas with negative feedback it falls to 50. If due to ageing the amplifier gain falls to 80, obtain the Percentage reduction in stage gain (i) Without Feedback and (ii) With Negative Feedback. (6)

b. What is an Emitter Follower? Why is it so called? Draw the circuit diagram of an Emitter Follower using BJT and discuss its working. Also show that this circuit Provides High Input Impedance and Low Output Impedance. (10)

Q.6 a. compute the Frequency of Oscillations when a Phase-Shift Oscillator has R = 10 K, C = 0.01 F and RC = 2.2 K . What will be the minimum current gain needed for this purpose? (5)

b. discuss how a OP-AMP can be used to sum a number of input voltages applied to the Inverting terminal. How will you use the circuit to obtain the avg. of Input Voltages? (7)

c. What do you mean by Input Offset Current in OP-AMP? What is its reason and how is it Minimized? (4)

Q.7 a. What is Schmitt Trigger and explain its characteristic? How would you convert a Transistorized Bistable Multivibrator into Schmitt Trigger? (9)

b. Draw the circuit diagram of Collector coupled Astable Multivibrator using NPN transistors and discuss its operation. obtain the frequency and duty cycle of the Astable Multivibrator Output, if R1 = 10K, R2 = five K and C1 = C2 = 0.1F. (7)

Q.8 a. Draw a neat circuit diagram of Transistor (Silicon) Shunt Voltage Regulator. Use the subsequent data in your circuit: VZ = 8.3 V, Vin = 22 V, RS = 130 and RL = 100. Determine the (i) Regulated Voltage and (ii) Collector current. Also provide its drawbacks. (7)

b. Draw the circuit of Centre-Tap Full Wave Rectifier using capacitor filter and discuss its working by drawing input and output waveforms. (9)

Q.9 a. State and Prove De-Morgans Theorems. (5)

b. What is a Flip-Flop? What is the difference ranging from a Latch and a Flip-Flop? (4)

c. What is an Asynchronous Counter? Draw the Logic Diagram of 3-bit Ripple Counter and discuss its operation with the help of Timing Diagrams and Truth Table. (7)

Earning:   Approval pending.