Diode

A diode is a two terminal electronic component that conducts electric current primarily in one direction, offering low resistance to current flowing one way and high resistance to current flowing the other way. The asymmetric conduction that makes a diode work was discovered by the German physicist Ferdinand Braun in 1874, in the contact between a crystalline mineral and a metal, and a semiconductor diode, the most common type used today, is a crystalline piece of semiconductor material, typically silicon, with a p-n junction connected to two terminals. An older form, the thermionic diode, is a vacuum tube with a heated cathode and a plate, in which electrons can flow only from the cathode to the plate. Diodes are used in rectifiers that convert alternating current to direct current, in demodulation in radio receivers, and, in the light emitting diode variant, as a light source and status indicator on electronic devices.