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N.B. : 1. Question ONE is compulsory.
Solve any THREE out of remaining questions.
Draw neat and clean diagrams.
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