Application of diac

Answer 1

The diac acts like an open-circuit until its switching or breakover voltage is exceeded. At that point the diac conducts until its current reduces toward zero (below the level of the holding current of the device). The diac, because of its peculiar construction, does not switch sharply into a low voltage condition at a low current level like the SCR or triac. Instead, once it goes into conduction, the diac maintains an almost continuous negative resistance characteristic, that is, voltage decreases with the increase in current. This means that, unlike the SCR and the triac, the diac cannot be expected to maintain a low (on) voltage drop until its current falls below a holding current level.

Answer 2

Diacs are used in AC circuits to control current flow in both directions, typically in applications that require bidirectional conduction such as lighting control and motor speed control. They can act as triggering devices for thyristors like TRIACs and can help regulate power in AC circuits with varying loads.