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AND gate
From Wikipedia, the free encyclopedia
| 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.
Contents |
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
Equation:- output(C) = i/p(A)+ i/p(B).
AND Gates are basic logic gates, and are implemented in both TTL and CMOS technology ICs. The '4000 series' CMOS IC AND gate device is designated the 4081, which includes four independent, two-input, AND gates.
This device is available from most semiconductor manufacturers. It is usually available in both through-hole DIP and surface mount packages such as SOIC. 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.
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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.
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.
- ^ Mano, M. Morris and Charles R. Kime. Logic and Computer Design Fundamentals, Third Edition. Prentice Hall, 2004. p. 73.