question_answer

The truth table for a logic gate is:

Input Output A B Y 1 1 0 0 1 1 1 0 1 0 0 1 The logic gate is:                                                                                                     [AIPMT 2002]

A)        NAND gate    

B)   XOR gate

C)  NOR gate     

D) OR gate

Correct Answer: A

Solution :

The given truth table is for NAND gate. The output for NAND gate is 1 only when one of its inputs is zero.

The Boolean expression for NAND gate is

\[Y=\overline{A\,.\,B}\]

That is   \[\overline{1\,.1}=\bar{1}=0\]

\[\overline{0\,.1}=\bar{0}=1\]

\[\overline{1\,.0}=\bar{0}=1\]

\[\overline{0\,.0}=\bar{0}=1\]

Note:    The symbol for NAND gate can be shown as: