ECA IMPORTANT QUESTIONS(FROM FIRST FOUR UNITS)

1. a. Draw the circuit diagram of Common Base amplifier and derive an

expression for its Voltage gain. b. The h-parameters of the transistor used in CE amplifier are hfe = 50,

hie=1.1K Ω , hre = 2.5x10-4, hoe = 24μ A/V. Find out current gain and voltage gains with and without source resistance, input and output impedances, given that RL= 10K and RS= 1 K

2. a. For a single stage transistor amplifier, RS = 10K and RL= 10K. The h-

parameter values are hfc = -51, hic =1.1K; hrc =1; hoc = 25µA/V Find AI ; AV ;AV S, Ri, and Ro for the CC transistor configuration.

b. For a single stage transistor amplifier, RS=1K; and RL= 10K The h-parameter values are hfe = 50, hie =1.1K; hre = 2.5x10-4, hoe = 25µA/V. Find AI ;AV ;AV S, Ri, and Ro for the CE transistor configuration.

3. a. Mention typical values for the h-parameters of a transistor connected in

CE, CB, and CC configurations. Compare the characteristics of CE, CB and CC amplifiers.

b. A 1- stage CE amplifier with emitter bypass resistor circuit has R1 = 50, R2 = 2K, RC = 1K, RE = 270, RS = 1K, RL = 1.2K. Find Ai, Ri, Ro, AV . The h-parameters are hie = 1100, hfe = 50, hoe = hre = 0.

4. a. Draw the circuit diagram of Darlington emitter follower and derive

expressions for current gain and input impedance. List the important characteristics of it.

b. If six identical amplifiers are cascaded, each having fH =100 KHz, determine the overall fH. Assume non interacting stages.

c. Write a short note on Gain-Bandwidth product of amplifiers.5.

a. What is the role of fT in defining the frequency range for the validity of Hybrid- π model of a transistor?

b. Show that rb′e in Hybrid - π model, is directly proportional to temperature and inversely proportional to collector current.

6. a. What are the specifications of amplifiers? Explain them. Give their

typical values. b. The LF parameters of a transistor at Ic = 20mA, Vce = 10V and at room

temperature hie = 400 , hoe = 10-5 µA/V , hfe = 150, hre = 10-4 . At the same operating point ft = 60 MHz, and Cob = 3PF , compute the values of all the hybrid-п parameter

7. a. When 2-stages of identical amplifiers are cascaded, obtain the

expressions for overall voltage gain, current gain and power gain. b. Four identical cascaded stages have an overall upper 3-dB frequency of

20 KHz and a lower 3-dB frequency of 20 Hz. What are fL and fH of each stage? Assume non interacting stages.

8. a. Derive various Resistive parameters of Hybrid - π model of a transistor

in terms of h parameters. b. What is the relationship between fT and fβ? Discuss the significance of fT

9.

a. Draw the circuit of Darlington emitter follower. Explain why the input impedance is higher than that of a single-stage emitter follower.

b. Draw the circuit diagram of Common Drain amplifier and derive an expression for its Voltage gain.

10. a. Draw the circuit of a CS amplifier and its low frequency small signal

equivalent circuit. Derive the expression for its voltage gainb. Obtain the expression for voltage gain of the common source amplifier

with current-source load.c. Explain in detail about cascode amplifiers.