GATE Electrical 2014 Set 3 | Question: 21

Question

A state diagram of a logic gate which exhibits a delay in the output is shown in the figure, where $X$ is the don’t care condition, and $Q$ is the output representing the state.

The logic gate represented by the state diagram is

• A. $XOR$
• B. $OR$
• C. $AND$
• D. $NAND$

Answer 1

Ans is D )

Becoz Nand output will be zero only when input is 11.

Also for input
0 1

0 0

output is 1 and it can be written as 0X ( x is don't care).

THIS shows that this is Nand Not XOR becoz In XOR for 0,0 output will be 0 .

It can also be derived using truth table .