Diode

A device with a structure in which two types of semiconductors, P-type and N-type, are joined together. It has two electrodes: the anode on the P side and the cathode on the N side. When a positive voltage is applied to the anode and a negative voltage to the cathode, current flows from the P side to the N side; this direction is called forward bias. Conversely, when a negative voltage is applied to the anode and a positive voltage to the cathode, a depletion layer forms at the PN junction and no current flows; this direction is called reverse bias. Taking advantage of the property that this diode allows current to flow in only one direction, it is widely used in switching power supply circuits, including rectifier circuits, and is one of the most basic and important components. Furthermore, when the reverse voltage is increased, current suddenly begins to flow at a certain value. This phenomenon is called breakdown (Zener effect), and the voltage at that time is called the Zener voltage. A special diode that utilizes this breakdown phenomenon to allow current to flow in the reverse direction is called a Zener diode.