DIACs
A DIAC, short for Diode for Alternating Current, is a bidirectional trigger diode used primarily to gate TRIACs in alternating-current circuits. It is a two-terminal device with a four-layer PNPN structure and is designed to conduct in either direction only after a characteristic breakdown (breakover) voltage is reached. Once the breakover voltage is exceeded, the DIAC conducts a sharp, short current pulse and then returns to a high-impedance state when the current falls below its holding value.
In typical use, a DIAC is part of a triggering network for a TRIAC in phase-control applications
Key characteristics include a breakover voltage that varies by type (commonly around 28–32 V for standard DB3
Common types include DB3, DB4, and DB5, offered in small epoxy or glass packages. They are widely