What is the gate in this SIDAC for

[ren_zokuken01]

https://www.pwrx.com/pwrx/docs/bs08d.pdf

What exactly is the gate on this SIDAC for? I thought SIDAC normally doesn't have any gates.

 

[ren_zokuken01]

Is the gate when pulled up the SIDAC can breakdown, but when pulled down it won't?

 

[vtech]

The Powerex device is not a Sidac.
It is a Silicon Bilateral Switch.
Similar to a Sidac except highly symmetrical in operation which can be modified by means of a gate pin.

 

[ren_zokuken01]

Uhhh, Digikey listed it under Sidac/Diacs and the description said "SIDAC 7-9V 1A TO92", so I believed them.

 

[ren_zokuken01]

OK, so to be clear, the voltage breakdown of the device becomes the rated voltage breakdown (typically 8V, in the datasheet) minus the gate voltage?

 

[vtech]

Not sure what you mean by subtracting gate voltage?
As a bilateral device meaning it can conduct either way. There is no anode/cathode hence calling either side terminals 1,2.
Depending on your circuit wiring, threshold of plus or minus 8 volts w/specific hold current is needed to fire up the device.
Look at the characteristic curve. Gate break over voltage on either side and once turned on, it almost behaves like a short.

 

[Tony Stewart]

Being a symmetrical device, having the gate allows it to cut the Vs by 50% vs not having a gate and just assuming they are perfectly symmetrical and the centre voltage Vs is 1/2 (Vt1-Vt2)
So an enhanced SIDAC if you like.

 

[ren_zokuken01]

So it's like a potentiometer with its adjustable center tap and 2 extreme terminals? The voltage drop between the tap and one of the terminal determines the voltage breakdown for that side of the device.