The DIAC is a full-wave or bi-directional semiconductor switch that can be turned on in both forward and reverse polarities. DIode Alternating Current (DIAC) is widely used to assist even triggering of a TRIAC (or a thyristor). DIAC is composed by three layers (PNP), very much similar to a transistor, however, the doping concentrations in N –type crystal are different. A pair of diodes of four layers in parallel is an equivalent circuit of a DIAC. Typically the DIAC is placed in series with the gate of a TRIAC. DIACs are often used in conjunction with TRIACs because these devices do not fire symmetrically as a result of slight differences between the two halves of the device.
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Capacitor
The phenomenon of conductivity in only one direction is used as an electrical current switching for rectification of half-wave, so, this is the most used diode effect in electronics, because allows the current to flow between its terminals in only one direction. This property is used in many electronic circuits (and rectifiers).
A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction.
At some point, the potential formed by the pn junction don’t allow the electrons and gaps move.