Let us discuss about logical NAND gate
When output of an AND gate is inverted through a NOT gate, the operation is called NAND operation
The logic gate which performs this NAND operation is called NAND gate
A NOT gate followed by an AND gate makes a NAND gate
The basic logical construction of the NAND gate is shown here in this figure
The symbol of NAND gate is similar to the symbol of AND gate but one bubble is drawn at the output point of the AND gate in the case of NAND gate
Truth table of a NAND gate is shown here. Here, output is whole bar of A.B. Here, when A and B both are 0, the output is 1. When A is 0 and B is 1, the output is 1. When A is 1 and B is 0, the output is 1. And when both A and B are 1, the output is 0
It is just reverse of the truth table of AND gate where output is A.B. Here, when A and B both are 0, the output is 0. When A is 0 and B is 1, the output is 0. When A is 1 and B is 0, the output is 0. And when both A and B are 1, the output is 1
NAND gate actually means NOT AND gate which means the output of this gate is just reverse of that of a similar AND gate. We know that the output of the AND gate is only high or 1 when all the inputs are high or 1. In all other cases, the output of AND gate is low or 0
In the case of NAND, the case is just opposite. Here, the output is only low or 0 when and only when all outputs of the gate are 1 and in all other cases, the output of NAND gate is high or 1