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Gate current and triggering quadrants

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Figure 11. AC switches symbols

Four triggering quadrants can be defined according to the polarity of the gate current and

the polarity of the voltage applied across the device, as shown in Figure 12.

Figure 12. Triac triggering quadrants

For an SCR, only a positive gate current can switch-on the device. Thus, the triggering

quadrants are not considered for SCR devices.

The usable triggering quadrants depend on the family and the class of the device used. The

table 2 sums-up the triggering quadrants for STMicroelectronics devices.

A2

Out

Out

G

G

G

A1

Com

Com

Triac

ACST

ACS

+ +

--

+-

1 st

2 nd

3 rd

4 th

V T

I G

A 2 (or OUT)

I G

V T

A 1 (or COM)

-+

G