Universal Logic Gates (NAND, NOR Gate)

Universal Gates are the logic gates from which all the basic logic gates can be derived. They can implement any Boolean function without requiring any other gate. Universal Gates can realize all the binary operations.

There are following two universal logic gates- 

• NAND Gate
• NOR Gate

1) NAND Gate

A NAND Gate is an AND Gate followed by a NOT Gate. It’s outputs are opposite of an AND Gate The output of NAND gate is high (1) when at least one of its inputs is low (0).

When all of its inputs are high (1) then the output of NAND gate is low (0)

Logic Expression

F = (A.B)’ = A’ + B’

Logic Symbol

 The logic symbol for NAND Gate is given below:

Truth Table

NAND GATE as Universal Gate :

• NAND Gate as NOT Gate

• NAND Gate as AND Gate

• NAND Gate as OR Gate

2) NOR Gate

A NOR Gate is an OR Gate followed by a NOT Gate. It’s outputs are opposite of an OR Gate. The output of NOR gate is high (1) if all of its inputs are low (0) AND, and when any of its inputs is high (1) then its output is low (0).

Logic Expression

F = (A+B)’ = A’.B’

Logic Symbol

 The logic symbol for NOR Gate is given below:

Truth Table

NOR GATE as Universal Gate :

• NOR Gate as NOT Gate

• NOR Gate as OR Gate

• NOR Gate as AND Gate