MOSFET-- what happens if voltage is reversed?

Other Hardware General Electronics
1

I want to use an N-channel power MOSFET in a mode where the drain-source voltage may be reversed part of the time. The MOSFET will be used as a switch, so part of the time, it will be fully on, and otherwise, fully off. During both the on and off portions of its operation, the voltage applied may be reversed from the correct drain-source polarity.

I've been unable to find much explanation of this. Does current flow in the reverse direction? Will the MOSFET disappear in smoke. If you know of or can provide an explanation of this, I'd appreciate it.

Thanks in advance for any information.

2

Which MOSFET? Most have an inherent diode that will conduct in the opposite direcetion if the voltage is reversed.

3

jrdoner:
Does current flow in the reverse direction?

Yes

(most likely).

jrdoner:
Will the MOSFET disappear in smoke.

Depends on how many amps are available from your power supply.

4

All power MOSFETs have a diode as part of their very structure, so they always
conduct in reverse.

For AC switching you need a triac, or a pair of n-MOSFETs source-to-source
with a floating supply to drive the gates.

5

MarkT:
All power MOSFETs have a diode as part of their very structure, so they always
conduct in reverse.

For AC switching you need a triac, or a pair of n-MOSFETs source-to-source
with a floating supply to drive the gates.

I'd prefer triac or a pair of thryristors.

6

Each have their own plus and minus points - MOSFETs can run much cooler,
can be turned off at any time, but are less robust. Triacs/thyristors only turn
off at current zero crossings...