Triac

The bi-directional thyristor (TRIAC) is composed of NNPPN five-layer semiconductor material with three electrodes (main electrode T1, main electrode T2 and gate G), which is equivalent to two anti-parallel common unidirectional thyristors (SCR).

Compared with unidirectional thyristors, the main differences between SCR and are:

The trigger voltage is non-polar, and the TRIAC will be turned on as long as the absolute value of trigger voltage reaches the trigger threshold;

After triggered, TRAIC can be conducted bi-directionally.