Electronics and Communication Engineering - Exam Questions Papers

26. 

The following circuit represents :

A. A(B + CD) BC
B.
C. AB + BC + ACD
D. none of these

Answer: Option A

Explanation:


27. 

In the circuit shown below current through the resistor is shown. Voltage across 4 Ω resistor is:

A. 8 volt
B. ≈ 5.87 V
C. ≈ 6.87 V
D. None of these

Answer: Option B

Explanation:

Voltage across 5 Ω = 10 V

Thus voltage across 7 Ω = 10 V (5 Ω || 7 Ω)


28. 

If the function A, B are A = R + PQ + RS B = PQRS + PQRS + PQRS
Which of the following is true?

A. A = B
B. A = B
C. no direct relation between A and B
D. insufficient data

Answer: Option B

Explanation:

A = R + PQ + RS

B = PQ R S + P Q R S + PQ R S


29. 

In 8085 microprocessor system, what will be the total delay provided by the following loop.
MVI A, 11H
LXI B, 12FFH
Delay: DCX B
XTHL
NOP
XRA B
JNZ Delay

where system clock is operating at 3 MHz.

A. 3.154 msec
B. 3.514 msec
C. 2.644 msec
D. 3.166 msec

Answer: Option A

Explanation:

8085 T-States

MVI A, 11H 7

LX1 B, 12FFH 10

Delay: DCX B 6

XTHL 16

NOP 4

XRA B 4

JNZ Delay 10/7

Total T states = 7 + 10 + 255(6 + 16 + 4 + 4 + 7) + 10 = 9462

Therefore total delay introduced = = 3.154 m sec.


30. 

A speech signal, band limited to 4kHz and peak voltage varying between + 5V and - 5V is sampled at the Nyquist rate. Each sample is quantized and represented by 8 bits. The number of quantization levels required to reduce the quantization noise by a factor of 4 would be

A. 1024
B. 512
C. 256
D. 64

Answer: Option B

Explanation:

To reduce quantization noise by 4

No. of levels should increase by 2

Thus 512 levels are required.