PHYS345 Electricity and Electronics


[Schematic of NAND gate]

A: B: C:
(in) (in) (out)
0 0 1
0 1 1
1 0 1
1 1 0

Please note the connection between the NAND and the AND gate. The output of the NAND gate is opposite of the AND gate -- NAND stands for NOT AND. In digital logic NOT represents the opposite -- NOT true is false, NOT 1 is 0. The symbol for NOT is a bar over whatever quantity is being "NOTed." Compare the schematic symbols for NAND and AND -- the "bubble" near the output of the NAND gate represents the NOT operation.

The NAND is one of the binary operations most heavily used in digital logic, an operation involving two input states, resulting in one of two possible output states. These electronic circuits are known as gates because they control the flow of bits (information) through the overall circuit.

Note that the truth table is independent of fabrication details; i.e. whether it is a CMOS gate or from a different logic "family" does not change the logic of the operation -- the actual gate is constructed to create the desired truth table.

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Last updated Oct. 27, 1998.
Copyright George Watson, Univ. of Delaware, 1998.