On Feb 26, 2005, at 1:40 PM, Wouter van Ooijen wrote:

> it is not the P-FET that is on (conducting) that gets hot,
> it is the other one, who is supposed to be off!
>
You're counting on the ULN2003 to pull down the gate and turn
off the MOSfet, but the ULN is a darlington with a relatively
significant Vce (1V or so) - does that end up leaving the MOSFET
partially on?  (If so, the other side of the bridge provides
plenty of "load" to make it get hot...

Isn't the ULN an odd choice for driving an H-bridge?  I would have
thought you'd want some sort of push-pull driver rather than
something open-collector (but I haven't designed any successful
H-bridges, either.)

BillW

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