I didnt think it had to be a difficult problem, but I thought there was
a chance there were devices out there that fit the bill, and someone
might have some useful suggestions. I'd like to keep the parts count
down to two, and have yet to think of an implementation that would
operate the gate, but haven't put myself to task either. One
consideration is the mosfet needs to be set up in a way that it
defaults to ON in most conceivable failures within the circuit that
drives it.. A current sense resistor voltage, amplified, on a
comparator that drives an optoisolator that pulls that gate low..
otherwise held high by pullup resistor, with some RC nudging into the
region of desired times.
