INPUT OUTPUT
A B A AND B
0 0 0
0 1 0
1 0 0
1 1 1

The AND gate is a digital logic gate that implements logical conjunction - it behaves according to the truth table to the right. A HIGH output (1) results only if both the inputs to the AND gate are HIGH (1). If neither or only one input to the AND gate is HIGH, a LOW output results.

Symbols[edit | edit source]

There are two symbols for AND gates: the 'military' symbol and the 'rectangular' symbol. These are also known as the 'American' and 'British' symbols. For more information see Logic Gate Symbols


'Military' AND Symbol

'Rectangular' AND Symbol


File:CMOS 4081 diagram.svg

This schematic diagram shows the arrangement of AND gates within a standard 4081 CMOS integrated circuit.

Hardware Description and Pinout[edit | edit source]

AND Gates are basic logic gates, and as such they are recognised in TTL and CMOS ICs. The standard, 4000 series, CMOS IC is the 4081, which includes four independent, two-input, AND gates.

This device is available from most semiconductor manufacturers such as Philips. It is usually available in both through-hole DIL and SOIC format. Datasheets are readily available in most Datasheet Databases.

As well as the standard 2-Input AND Gate, 3-, 4- and 8-Input AND Gates are also available:

  • 4073: Triple 3-Input AND Gate
  • 4082: Dual 4-Input AND Gate
  • An 8-Input NAND Gate exists (4068), and this is easily made into an 8-Input AND gate by inversion of the output.

Implementations[edit | edit source]

File:NMOS AND.png File:PMOS AND.png An AND gate is usually designed using NMOS or PMOS MOSFETs as shown in the schematics to the left. The digital inputs a and b cause the output F to have the same result as the AND function.

Alternatives[edit | edit source]

File:AND from NAND.svg

AND Gate Constructed Using Only NAND Gates

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] which can be used to make all the others. The configuration shown on the right shows how to use NAND gates to create the effect of an AND gate.

See also[edit | edit source]

References[edit | edit source]

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