N.B. : 1. Question ONE is compulsory.

1. Solve any THREE out of remaining questions.

2. Draw neat and clean diagrams.

3. Assume suitable data if required.

Q.1

A: What is the source of the leakage current in a transistor? If the emitter current of a transistor is 8mA and 1/100 of lc, determine the levels of Ic and In. 5

B: Explain the concept of virtual ground in operational amplifiers. 5

C: Draw the spectrum of amplitude modulated wave and explain its components. 5

D: Explain adaptive delta modulation. 5

Q.2

A: The emitter bias configuration as shown in following figure has the specifications:

.ICQ =$\frac{1}{2}$ Icsat . Icsat = 8mA Vc = 18V and β = 110

Determine Rc, RE and Rs. 10

B: Explain the following parameters and their values for 741 opamp

CMRR, Slew Rate, Gain Bandwidth Product, Input Offset Voltage and Output Resistance. 10

Q.3

A: Given β = 120 and IE = 3.2 mA for a common-emitter configuration with r0 = ∞Ω,

Determine:

(a) Zi

(b) Av if a load of 2 k Ω is applied

(c) Ai with the 2 k Ω load. 5

B: State and explain Barkhausens criteria for oscillations. 5

C: Explain principle of TDM. 5

D: Determine the output voltage for the circuit if V1=5V and V2=3V

Q.4

A: Draw the block diagram of phase cancellation SSB generation and explain how the

carrier and unwanted sidebands are suppressed. 10

B: Draw the PAM, PPM and PWM waveforms in time domain assuming a sinusoidal

Modulating signal. Explain them in brief. 10

Q.5

A: State Shannon’s theorem on channel capacity.

What is the maximum capacity of a perfectly noiseless channel whose bandwidth

Is 120 Hz, in which the values of the data transmitted may be indicated by any one of the

10 different amplitudes? 10

B: With respect to neat diagram explain elements of analog communications system. 10

Q.6

A: What is Nyquist Criteria? What is the significance? 5

B: Give the proper definition for entropy and information rate. 5

C: Write short note on op-amp as comparator. 5

D: Differentiate between Class A and Class C power amplifiers with respect to circuit diagram, operating cycle and power efficiency. 5