and gate

Information about and gate

INPUTOUTPUT
ABA AND B
000
010
100
111


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

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

'Rectangular' AND Symbol


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

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.

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

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

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.
Enlarge picture
AND Gate Constructed Using Only NAND Gates

See also

References

1. ^ Mano, M. Morris and Charles R. Kime. Logic and Computer Design Fundamentals, Third Edition. Prentice Hall, 2004. p. 73.
A logic gate performs a logical operation on one or more logic inputs and produces a single logic output. The logic normally performed is Boolean logic and is most commonly found in digital circuits.
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In logic and/or mathematics, logical conjunction or and is a two-place logical operation that results in a value of true if both of its operands are true, otherwise a value of false!

Definition

Logical conjunction
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Complementary metal–oxide–semiconductor (CMOS) ("see-moss", IPA: /ˈsiːmɒs/), is a major class of integrated circuits.
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integrated circuit (also known as IC, microcircuit, microchip, silicon chip, or chip) is a miniaturized electronic circuit (consisting mainly of semiconductor devices, as well as passive components) that has been manufactured in the surface of a
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DIP14-Package]] In microelectronics, a dual in-line package (DIP), sometimes called a DIL package, is an electronic device package with a rectangular housing and two parallel rows of electrical connecting pins, usually protruding from the longer sides of the package
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A Small-Outline Integrated Circuit (SOIC) is an integrated circuit (IC) package which occupies an area about 30 - 50% less than an equivalent DIP, with a typical thickness that is 70% less. They are generally available in the same pinouts as their counterpart DIP ICs.
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The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is by far the most common field-effect transistor in both digital and analog circuits.
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OR gate is a digital logic gate that implements logical disjunction - it behaves according to the truth table to the right. A HIGH output (1) results if one or both the inputs to the gate are HIGH (1). If neither input is HIGH, a LOW output (0) results.
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The NOT gate or inverter is a digital logic gate that implements logical negation. It behaves according to the truth table to the right. A HIGH output (1) results if the inputs is LOW (0).
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This article is about NOR in the sense of an electronic logic gate (e.g. CMOS 4001). For NOR in the purely logical sense, see Logical NOR, for other uses of similar terms, see Nor.

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XOR gate is a digital logic gate that implements exclusive disjunction - it behaves according to the truth table to the right. A HIGH output (1) results if one, and only one, of the inputs to the gate is HIGH (1).
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A logic gate performs a logical operation on one or more logic inputs and produces a single logic output. The logic normally performed is Boolean logic and is most commonly found in digital circuits.
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