Editing TRIAC (section)

===Quadrant 2===
[[file:Triac Quad II.svg|thumb|Figure 5: Operation in quadrant 2]]

Quadrant 2 operation occurs when the gate is negative and MT2 is positive with respect to MT1.<sup>[[#figure1|Figure 1]]</sup>

Figure 5 shows the triggering process. The turn-on of the device is three-fold and starts when the current from MT1 flows into the gate through the p-n junction under the gate. This switches on a structure composed by an NPN transistor and a PNP transistor, which has the gate as cathode (the turn-on of this structure is indicated by "1" in the figure). As current into the gate increases, the potential of the left side of the p-silicon under the gate rises towards MT1, since the difference in potential between the gate and MT2 tends to lower: this establishes a current between the left side and the right side of the p-silicon (indicated by "2" in the figure), which in turn switches on the NPN transistor under the MT1 terminal and as a consequence also the pnp transistor between MT2 and the right side of the upper p-silicon. So, in the end, the structure which is crossed by the major portion of the current is the same as quadrant-I operation ("3" in Figure 5).<ref name="PowerElec"/>