Construction of TRIAC ( triode for alternating current)

 Three terminals - TRIAC

Three terminals – TRIAC

The TRIAC stands for triode for alternating current. It is another thyristor family device which is used extensively for the control of power in A.C. circuits. The TRIAC is bidirectional device and when in operation, it is equivalent to two silicon controlled rectifiers (SCRs) connected in anti parallel. It has a four layer (PNPN) and three junction devices. It has  three terminals designated as a main terminal 1 (MT1), main terminal 2 (MT2) and gate G. We can  see that the terminal MT2 is common to N4 as well as P1, the terminal MT1 is common to N2 as well as P2 and G is common to N3 as well as P2. This different  type of  construction of TRIAC makes it suitable to be operated in four modes. The TRIAC is turned ON by applying a positive or negative voltage to the gate with respect to MT1.


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