Thyristor Semiconductor Products Page 19 Thyristor

2014 Littelfuse, Inc. Specifications are subject to change without notice. Revised: 12/14/14 Teccor brand Thyristors AN1001 Triac Basic Operation Figure AN1001.4 shows the simple block construction of a Triac. Its primary function is to control power bilaterally in an AC circuit. N P N P Block Construction Main Terminal 2 (MT2) Gate Schematic Symbol MT1 Gate MT2 Main Terminal 1 (MT1) MT1 MT2 Figure AN1001.4 Triac Block Construction Operation of a Triac can be related to two SCRs connected in parallel in opposite directions as shown in Figure AN1001.5. Although the gates are shown separately for each SCR, a Triac has a single gate and can be triggered by either polarity. Figure AN1001.5 SCRs Connected as a Triac Since a Triac operates in both directions, it behaves essentially the same in either direction as an SCR would behave in the forward direction (blocking or operating). Geometric Construction Figure AN1001.6 show simplified cross-sectional views of a Triac chip in various gating quadrants and blocking modes. N P GATE(+) MT1(-) I GT N I T MT2(+) QUADRANT I GATE(-) MT1(-) MT2(+) QUADRANT II I GT Blocking Junction MT2(+) MT1(-) Equivalent Diode Relationship N P GATE(+) MT1(+) I GT QUADRANT III GATE(-) MT1(+) MT2(-) QUADRANT IV Blocking Junction Equivalent Diode Relationship I T I T I GT MT1(+) MT2(-) Figure AN1001.6 Simplified Cross-sectional of Triac Chip Fundamental Characteristics of Thyristors (continued)

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