rectifier

Device for obtaining one-directional current (DC) from an alternating source of supply (AC). (The process is necessary because almost all electrical power is generated, transmitted, and supplied as alternating current, but many devices, from television sets to electric motors, require direct current.) Types include plate rectifiers, thermionic diodes, and semiconductor diodes.

A single diode produces half-wave rectification in which current flows in one direction for one-half of the alternating-current cycle only - an inefficient process in which the power is effectively turned off for half the time. A bridge rectifier, constructed from four diodes, can rectify the alternating supply in such a way that both the positive and negative halves of the alternating cycle can produce a current flowing in the same direction.