NAND gate

A NAND gate is a logic gate used to build digital logic circuits. It is a combination of an AND and NOT gate. The name refers to this. The NAND gate is a “universal gate”, that means all other types of logic gates can be obtained by wiring exclusively one or more NAND gates in a particular manner.

Behavior

Given two inputs, A and B, A NAND B will be true if at most one of A and B is true. In other words, A NAND B is false if both A and B are true, and true otherwise.

INPUT		OUTPUT
A	B	A ⊼ B
0	0	1
0	1	1
1	0	1
1	1	0

Symbols

There are three symbols for drawing NAND gates in electrical circuit schematics: the "distinctive shape" symbol, the “military” symbol, and the “rectangular” symbol. For more information see logic gate symbols.

• 
  “Distinctive shape” NAND symbol, also that used by US ANSI
• 
  “Military” NAND symbol, also that used by DIN
• 
  “Rectangular” NAND symbol, used by IEC

Application

Since a NAND gate is a universal gate, microprocessors can be built using this type of gate only. For example:

• the negation can be represented by ¬A ≡ A ⊼ A
• and the disjunction can be obtained by A ∨ B ≡ (A ⊼ A) ⊼ (B ⊼ B)