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Uncle Jed, can you point to a document that mentions MOSFET gate dv/dt sensitivity? I have never heard of it. Vds dv/dt can be a problem.getting back to what was happening to the FET with the switch for a moment, i think the parameter you exceeded was the max dv/dt figure for the gate. in the data sheet it's most likely listed in volts/microsecond. exceeding the max dv/dt for the gate will cause the gate insulation to break down, even if you don't exceed the Vgs of the FET.
I hate to belabor this point, but why do you agree with this? Is it in the MOSFET's datasheet?UncleJed;"I think the parameter you exceeded was the max dv/dt figure for the gate." I agree!
As I said before, MOSFETs can be damaged by excessive dv/dt applied between drain and source.Reread post #28
**broken link removed**
"In the bottom left corner is an N FET drawing similar to what I had when I Killed my FETs, minus the cap. I figured there was something weird going on and the dv/dt sounds correct, I was suspecting that the gate was charging backwards (blue circle) when off and when the switch was closed, it discharged and recharged 'violently' punching a hole in the gate insulator and killing the FET.
originally attributed to noise, dv/dt makes real good sense to me. I reverse charged the gate with a diode checker and got conduction in one direction only, doing so with the power of closing a switch to, or touching a wire to, the gate would create a high dv/dt, considering dt is extremely small.
I guess I just believe that it was dv/dt that killed a couple of high power FETs when current was limited to < 1 amp! and no, I haven't been able to find any specs about dv/dt on the data sheet.
kinarfi
I ask as nicely as I can, would you please build the circuit referred to in previous post without the cap and attached and try it, see if you lose power FET also or not? and let me/us know. Remember, it's the closing of the switch after the gate has reversed charged that kills the FET. Good Luck.As I said before, MOSFETs can be damaged by excessive dv/dt applied between drain and source.
I'll just state unequivocally that MOSFETs cannot be damaged by excessive dv/dt applied between gate and source, and see if anyone can refute this.