AND gate

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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.

1 Symbols
2 Hardware Description and Pinout
3 Implementations
- 3.1 Alternatives
4 See also
5 References

[edit] Symbols

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

[edit] Hardware Description and Pinout

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. The pinout diagram is as follows:

Pinout Diagram of a 4081 Quad AND DIL-format IC

 1  Input A1
 2  Input B1
 3  Output Q1
 4  Output Q2
 5  Input B2
 6  Input A2
 7  Vss
 8  Input A3
 9  Input B3
 10 Output Q3
 11 Output Q4
 12 Input B4
 13 Input A4
 14 Vdd

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.

[edit] Implementations

An AND gate is usually designed using NMOS or PNOS 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.

[edit] Alternatives

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.