A diode is a two-terminal semiconductor device that conducts current primarily in one direction. The diode has very low resistance as current flows from the anode to cathode ends of the device, and very high resistance in the opposite direction, effectively making the diode a one-way conductor.

Diodes are among the most common semiconductor devices, because the one-way directional current provided by diodes is useful in all varieties of electronic applications. Diodes are used to convert alternating current to direct current, measure temperature, protect from overvoltage, and steer current.

Diodes can also be utilized as logic gates, and perform high speed switching functions.