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My understanding is that a MOSFET's Rdson generally decreases with higher absolute Vgs values within its specified range, and I typically consult datasheet curves showing Rdson vs Id and Vgs.

I'm looking at P-MOSFETS for an application with Vgs=-12V, and I'm noticing datasheets (e.g. ZXMP3A17E6) which have an absolute maximum Vgs of +/-20V, but Rdson is specified at values to Vgs=-10V, not beyond.

Is it safe to assume that Rdson at Vgs=-12V would be the same or lower than at -10V, or is it possible that it actually goes up in the -10 to -20V range?

Bonus question: I've been assuming I should stay away from FETs whose absolute maximum Vgs is 12V, figuring I should leave a margin of safety there, but I'm not sure if that's standard practice.

JAE
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Is it safe to assume that Rdson at Vgs=-12V would be the same or lower than at -10V

That's a fairly safe assumption but, that wouldn't satisfy me. I'd be looking for a MOSFET that has the graphs I need and the data I need. I'd pick a different MOSFET or, not drive the current MOSFET higher than 10 volts.

I may be being overly cautious in some people's eyes but, it's just not worth the risk.

I've been assuming I should stay away from FETs whose absolute maximum Vgs is 12V, figuring I should leave a margin of safety there, but I'm not sure if that's standard practice.

Everyone's different but, for me, I'd want to restrict my drive voltage to about two-thirds of the maximum limit voltage. So, for a limit of 20 volts, I wouldn't be too keen on driving it higher than 13.333 volts.

Andy aka
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