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The OR gate
OR gate
is a digital logic gate that implements logical disjunction â€“ 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. In another sense, the function of OR effectively finds the maximum between two binary digits, just as the complementary AND function finds the minimum.[1]

Contents

1 Symbols 2 Hardware description and pinout 3 Implementations

3.1 Alternatives

4 Wired-OR 5 See also 6 References

Symbols[edit] There are two symbols of OR gates: the American (ANSI or 'military') symbol and the IEC ('European' or 'rectangular') symbol, as well as the deprecated DIN
DIN
symbol.[2][3] For more information see Logic Gate Symbols.

MIL/ANSI Symbol IEC Symbol DIN
DIN
Symbol

This schematic diagram shows the arrangement of four OR gates within a standard 4071 CMOS
CMOS
integrated circuit.

Hardware description and pinout[edit] OR Gates are basic logic gates, and as such they are available in TTL and CMOS
CMOS
ICs logic families. The standard 4000 series CMOS
CMOS
IC is the 4071, which includes four independent two-input OR gates. The ancestral TTL device is the 7432. There are many offshoots of the original 7432 OR gate, all having the same pinout but different internal architecture, allowing them to operate in different voltage ranges and/or at higher speeds. In addition to the standard 2-Input OR Gate, 3- and 4-Input OR Gates are also available. In the CMOS
CMOS
series, these are:

4075: Triple 3-Input OR Gate 4072: Dual 4-Input OR Gate

Variations include:

74LS32: Quad 2-input OR gate
OR gate
(low power Schottky version) 74HC32: Quad 2-input OR gate
OR gate
(high speed CMOS
CMOS
version) - has lower current consumption/wider voltage range 74AC32: Quad 2-input OR gate
OR gate
(advanced CMOS
CMOS
version) - similar to 74HC32, but with significantly faster switching speeds and stronger drive 74LVC32: Low voltage CMOS
CMOS
version of the same.

Implementations[edit]

CMOS
CMOS
OR gate

NMOS OR gate

BJT OR gate

OR gate
OR gate
using diodes

Alternatives[edit] Further information: NAND logic
NAND logic
and NOR logic If no specific OR gates are available, one can be made from NAND or NOR gates in the configuration shown in the image below. Any logic gate can be made from a combination of NAND or NOR gates.

Desired gate NAND construction NOR construction

Wired-OR[edit]

Wired OR gate
OR gate
using open-collector NOR gates

With active low open collector logic outputs, as used for control signals in many circuits, an OR function can be produced by wiring together several outputs. This arrangement is called a wired OR. This implementation of an OR function typically is also found in integrated circuits of N or P-type only transistor processes.

See also[edit]

Wikimedia Commons has media related to OR gates.

AND gate NOT gate NAND gate NOR gate XOR gate XNOR gate Boolean algebra Logic gate

References[edit]

^ "OR Gate". Hyperphysics.phy-astr.gsu.edu. Retrieved 2012-09-24.  ^ Harris, David Harris, Sarah (2007). Digital design and computer architecture (1st ed.). San Francisco,Calif.: Morgan Kaufmann. p. 21. ISBN 9780123704979.  ^ Brumbach, Michael E. Industrial electricity (8th ed.). Clifton Park, N.Y.: Delmar. p. 546. ISBN 9781435483743. 

v t e

Logical connectives

Tautology/True 

displaystyle top

Alternative denial (NAND gate) 

displaystyle uparrow

Converse implication 

displaystyle leftarrow

Implication (IMPLY gate) 

displaystyle rightarrow

Disjunction (OR gate) 

displaystyle lor

Negation (NOT gate) 

¬

displaystyle neg

Exclusive or (XOR gate) 

displaystyle nleftrightarrow

Biconditional (XNOR gate) 

displaystyle leftrightarrow

Statement

Joint denial (NOR gate) 

displaystyle downarrow

Nonimplication 

displaystyle nrightarrow

Converse nonimplication 

displaystyle nleftarrow

Conjunction (AND gate) 

displaystyle land

Contradiction/False 

.