Electronics and Communication Engineering - Digital Electronics


A digital system is required to amplify a binary encoded audio signal. The user should be able to control the gain of the amplifier from a minimum to a maximum in 100 increments. The minimum number of bits required to encode, in straight binary is,

A. 8
B. 6
C. 5
D. 7

Answer: Option D


Let 6 bit required = 26 = 64, which indicate 64 increment.

If 7 bit = 27 = 128, for 100 increment, 7 bit required.


A 4 bit transistor register has output voltage of high-low-high-low. The binary number stored and its decimal equivalent are

A. 0101 and 5
B. 0101 and 10
C. 1010 and 5
D. 1010 and 10

Answer: Option D


1010 in binary and 8 + 2 = 10 in decimal.


Assertion (A): A demultiplexer cannot be used as a decoder

Reason (R): A multiplexer selects one of many outputs whereas a decoder selects on output corresponding to coded input.

A. Both A and R are correct and R is correct explanation of A
B. Both A and R are correct but R is not correct explanation of A
C. A is true, R is false
D. A is false, R is true

Answer: Option D


Demux can be used as a decoder.


Hexadecimal number F is called to octal number

A. 15
B. 16
C. 17
D. 18

Answer: Option C


F = 15 in decimal notation = 17 in octal notation (8 + 7 = 15).


A half adder can be used only for adding

A. 1 s
B. 2 s
C. 4 s
D. 8 s

Answer: Option A