Rushing

> > A gate-source clamp
> > zener pair (back to back ) may be needed to protect FETs against >
> > Vgsmax drive.

Zeners to ensure gate drive voltage does not exceed FET maximum
allowed - depends on FET and supply  and high side drive voltages.


> > I'd be slightly nervous about M3 connecting gates hard to ground - I'd
> > consider a series gate resistor. But logic says it's OK as is :-).
> >
>
> Sounds good. I put a 100k resistor between the gate and the mosfet.

Note potential time constants from R + C_FET

> Also to avoid the whole gate source problem, is there a way to bring out =
an
> "isolated" supply from the normal supply rail, so I can independently bia=
s
> the gate with an isolated ground on the source? Maybe using a switched
> capacitor method? Would there be ICs that do this?

Simple diode pump with 2 capacitor coupling. Similar circuit used for
floating panel meter supplies. Can supply cct later if needed. Rushing
....


Russell
--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.