Page 97 - Computer science 868 Class 12
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18. Draw the logic gate diagram for the reduced expression. Assume that the variables and their complements are available as
inputs. [ISC 2018]
Ans. Logic gate diagram:
A
B'
C'
F
D'
A'
C'
19. (a) What is an Encoder? Draw the Encoder circuit to convert A-F hexadecimal numbers to binary. State an application of a
Multiplexer. [ISC 2018]
Ans. An Encoder is a combinational circuit that convert decimal, octal or hexadecimal numbers to its equivalent binary form.
Circuit diagram to convert A-F hexadecimal numbers to binary:
A
B
C
D
E
F
Application of a Multiplexer:
1. Used for Routing of signals
2. Data Transmission
3. Telephone Exchanges/TV etc
(b) Using only NAND gates, draw the logic circuit diagram for A' + B. [ISC 2018]
Ans. Logic circuit diagram for A' + B using only NAND gates.
A
A' + B'
B
20. Name and draw the logic gate represented by the following truth table, where A and B are inputs and X is the output. [ISC 2019]
A B X
0 0 0
0 1 1
1 0 1
1 1 0
Ans. XOR Gate
A X
B
95
Computer Hardware 95

