Universal Gates

The NAND and NOR logic gates are called universal gates because any logic function can be realized using only  either NAND or  NOR gates.

1. NAND Gate

The NAND gate has two inputs and one output. The symbol of NAND gate is

(a) Symbol of NAND gate and (b) its equivalent representation

A NAND gate is equivalent to an AND gate followed by a NOT gate as illustrated in Fig. The Boolean  expression of the output (Y ) for a NAND gate is given as follows

The NAND logic is not associative. The NAND function with more than two inputs cannot be realized using  two-input NAND gates.

The truth table of NAND gate is

NOR Gate

The NOR gate has two inputs and one output. The symbols of NOR gate is

(a) Symbol of NOR gate and (b) its equivalent representation

A NOR gate is equivalent to an OR gate followed by a NOT gate as illustrated in Fig. 1.7(b). The Boolean  expression of the output (Y ) for a NOR gate is given as follows:

The truth table of NOR gate is

AND Gate  ,OR Gate,NOT Gate,XOR Gate,NAND Gate, NOR Gate

Universal Gates | NAND Gate | NOR Gate