Question

What is a NAND gate? Give its logic symbol.

Answer 1

To solve this question, it is important to understand the fact that there are two kinds of logic gates, namely – Basic Gates and Universal Gates. The understanding of the working of these gates are through truth tables, which tabulate the resultant output of any gate with all the permutations and combinations of the inputs to the logic gate.

Complete answer:
Logic gates are defined as the electronic circuits that have more than one input and only one output, whose relationship is dependent on an inherent logic of the logic gate. There are three basic logic gates: AND, OR and NOT. There are two more gates which are called Universal gates called NAND and NOR.
NAND and NOR gates are called universal gates since all the basic and advanced gates can be constructed using a combination of NAND gates.
Let us understand the details of NAND gate.
In NAND gate, the two inputs are multiplied and inverse is taken of the answer.
If A and B are two inputs to a NAND gate, the output is:
Here is the symbol for the NAND gate:

The truth table is as follows:

A	B	$\overline{A.B}$
0	0	1
0	1	1
1	0	0
1	1	0

Note: Here, we have seen that NAND and NOR gates can be performed as Universal Gates. Sometimes, it becomes difficult to remember the conversion of Universal gates into the basic AND and OR gates. You can easily remember the whole thing by understanding this following mnemonic.
NAND Gate:
To convert to AND gate, first negate together because AND means together and negate the result.

To convert to OR gate, first negate them individually because OR means individually and negate the result.