Characteristics: Triac - nptel
Characteristics: Triac - nptel
Characteristics: Triac - nptel
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G<br />
I G<br />
MT1<br />
( - )<br />
I G<br />
N 2<br />
I G<br />
I G<br />
N 3<br />
N 1<br />
MT1<br />
( + )<br />
P 2<br />
P 2<br />
N 1<br />
P 1<br />
P 1<br />
N 4<br />
(a)<br />
MT2<br />
( + )<br />
(b)<br />
MT2<br />
( - )<br />
Fig. 4.13: Conduction mechanism of a triac in trigger modes 1<br />
and 3<br />
(a) Mode – 1 , (b) Mode – 3 .<br />
In trigger mode-1 the gate current flows mainly through the P 2 N 2 junction like an ordinary<br />
thyristor. When the gate current has injected sufficient charge into P 2 layer the triac starts<br />
conducting through the P 1 N 1 P 2 N 2 layers like an ordinary thyristor.<br />
In the trigger mode-3 the gate current I g forward biases the P 2 P 3 junction and a large number of<br />
electrons are introduced in the P 2 region by N 3 . Finally the structure P 2 N 1 P 1 N 4 turns on<br />
completely.<br />
Version 2 EE IIT, Kharagpur 25
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