ORportti

ORportti, also written as OR-portti and in Finnish sometimes referred to as tai-portti, is a basic digital logic gate that performs the logical disjunction. It outputs a high signal when any of its inputs is high. For two inputs A and B, the output Q is true if A or B (or both) are true; equivalently Q equals A OR B. For n inputs, Q is true if at least one input is true. The only time the output is false is when all inputs are false.

In circuit diagrams, the OR portti is used to combine signals so that a single true result can be produced if any contributing signal is true. It is a fundamental building block in combinational logic and can be implemented with various technologies, including TTL and CMOS transistors. Multi-input OR gates extend the same principle to three or more inputs and may be realized with cascaded two-input gates or with dedicated multi-input transistor networks. Practical gates also have nonzero propagation delay and a limit on fan-out, which dictates how many subsequent inputs the gate can drive reliably.

The OR portti finds wide application in digital systems such as adders, data routing, control logic, and multiplexers. It often appears in combination with other gates to form more complex functions, such as enabling signals or constructing priority encoders. Historically, the concept derives from Boolean algebra developed by George Boole, with physical realizations appearing in early transistor logic and continuing into modern integrated circuits.

See also: logic gates, NOR gate, AND gate, NOT gate.