question_answer

Identify the logic gate from the following truth table:

Input		Output
A	B	Y
0	0	1
0	1	0
1	0	0
1	1	0

A)  NOR gate     

B)  NOT gate

C)  AND gate     

D)  NAND gate

Correct Answer: A

Solution :

NOR gate is a combination of OR gate and NOT gate. In other words, output of OR gate is connected to the input of a NOT gate as shown in figure. Note that output of OR gate is inverted to form NOR gate. This is illustrated in the truth table for NOR gate. It is clear that truth table for NOR gate is developed by inverting the output of the OR gate.

Input		Output
A	B	OR (Y)	NOR (Y)
0	0	0	1
1	0	1	0
0	1	1	0
1	1	1	0

The Boolean expression for NOR function is \[Y=\overline{A+B}\]