AND gate

The AND gate is a basic digital logic gate that implements logical conjunction - it behaves according to the truth table to the right. A HIGH output (1) results only if all the inputs to the AND gate are HIGH (1). If none or not all inputs to the AND gate are HIGH, a LOW output results. The function can be extended to any number of inputs.

INPUTOUTPUT
ABA AND B
000
010
100
111

Symbols

There are three symbols for AND gates: the American (ANSI or 'military') symbol and the IEC ('European' or 'rectangular') symbol, as well as the deprecated DIN symbol. Additional inputs can be added as needed. For more information see Logic Gate Symbols. It can also be denoted as symbol "^" or "&".

MIL/ANSI Symbol IEC Symbol DIN Symbol

The AND gate with inputs A and B and output C implements the logical expression . This expression also may be denoted as C=A^B or C=A&B.

Implementations

An AND gate is usually designed using N-channel (pictured) or P-channel MOSFETs. The digital inputs a and b cause the output F to have the same result as the AND function.

Analytical representation

is the analytical representation of AND gate:

Alternatives

If no specific AND gates are available, one can be made from NAND or NOR gates, because NAND and NOR gates are considered the "universal gates," [1] meaning that they can be used to make all the others.

Desired gateNAND constructionNOR construction

IC package

AND gates are available in IC packages. The 7408 IC is a well known QUAD 2-Input AND GATES and contains four independent gates each of which performs the logic AND function.

See also

References

  1. Mano, M. Morris and Charles R. Kime. Logic and Computer Design Fundamentals, Third Edition. Prentice Hall, 2004. p. 73.
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