A OR B
The 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.
There are two symbols for OR gates: the 'military' symbol and the 'rectangular' symbol. For more information see Logic Gate Symbols
Hardware Description and Pinout
This device is available from most semiconductor manufacturers. 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 OR Gate, 3- and 4-Input OR Gates are also available:
- 4075: Triple 3-Input OR Gate
- 4072: Dual 4-Input OR Gate
- 74LS32: Quad 2-input OR gate
If no specific OR gates are available, one can be made from NAND gates in the configuration shown below. Any logic gate can be made from a combination of NAND 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