A device that passes current in only one direction. A diode is usually a semiconductor. See the illustration. See also semiconductor.
Combination of a cold anode and a heated cathode (or the semiconductor equivalent, which incorporates a p–n junction). Either device allows the passage of direct current in one direction only, and so is commonly used in a rectifier to convert alternating current (AC) to direct current (DC).
1. A semiconductor that consists of a P-N junction; SYN. semiconductor diode, junction rectifier, crystal rectifier.
2. A thermionic tube having two electrodes; used as a rectifier; SYN. rectifying tube, rectifying valve.