Electronics and Communication Engineering - Exam Questions Papers

31. 

A delta modulation system is designed to operate at 3 times the Nyquist rate for a signal with a 3 KHz bandwidth. The quantization step size is 250 mv. The maximum amplitude of a 1 KHz input sinusoidal for which the delta modulator does not show slope overload is :

A. 716.2 mV
B. 500 mV
C. 647.87 mV
D. 400 mV

Answer: Option A

Explanation:

.


32. 

Values of iL, , VC and at t = 0 are given by,

A. 4 Amp, - 4 Amp/sec, 12 volts, - 4 volts/s
B. 4 Amp, 4 Amp/sec, -12 volts, - 12 volts/s
C. 6 Amp, - 2 Amp/sec, 0 volts, - 2 volts/sec
D. 6 Amp, 0 Amp/sec, - 2 volts, - 2 volts/sec

Answer: Option C

Explanation:

For t = 0 +

iL(0-) = = 6 A

VC(0-) = 0 V

For t = 0+

iL(0+) = 6

VC(0+) = 0

Apply KCL at node V

6 - V = (6 + v)2

6 - V = 12 + 2V

- 6 = 3V

V = VL = - 2V

At t = 0+, = -2

iL = 6 Amp

VC = 0 V

.


33. 

A continuous time LTI system is described by

Assuming zero initial conditions, the response y(t) of the above system for the input x(t) = e-2t u(t) is given by

A. (et - e3t) u(t)
B. (e-t - 3e-3t) u(t)
C. (e-t + e-3t) u(t)
D. (et + e3t) u(t)

Answer: Option B

Explanation:

y(t) = (e-t - e-3t) u(t).


34. 

The analog signal given below is sampled by 600 samples per second
m(t) = 2 sin 480pt + 3 sin 720pt
The folding (maximum) frequency is __________ .

A. 600 Hz
B. 120 Hz
C. 300 Hz
D. 360 Hz

Answer: Option C

Explanation:

Folding frequency (max.).


35. 

In the circuit shown, the power supplied by the voltage source

A. 0 W
B. 5 W
C. 10 W
D. 100 W

Answer: Option A

Explanation:

KVL → 10 = 2(i + 3) + 2(i + 2)

10 = 10 + 4ii = 0

Power = 0