Thanks David,

> I'd throw a scope on it and see why it's dying.
>
> Could be it's not turning on and off fast enough?  Linear region will cau=
se dissipation to skyrocket.
> I saw a case  where a FET was dying because of extremely short (100nS) tr=
ansients where the dissipation was over the limit.
>
> Could be a voltage spike from wiring inductance exceeding VDS.
>
> A Zener across VDS rated somewhat below the FET rating and above the powe=
r supply might help.
>
> Scope it and see.
You may have missed the original post. The FET is failing when the=20
output load is short circuited. During normal operation the fETs are=20
switching fine and all works perfectly.
Cheers,
Jim

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