At 01:51 PM 1/16/2007, Jinx wrote: >Can anyone recommend an on-line crash-course in FETs ? I hadn't >realised how many types there are until I had to look > >In this circuit I don't want to fiddle about making another voltage >for the gate (although the 12F would be capable of that), so would >like to be edumacated about FETs so I can pick one the engineer's >way instead of wussing out and going bipolar with a TIP If I can make what I think is a simple suggestion: use a capacitively coupled charge pump on the FET gate(2 caps, 2 diodes) and then have the 12F generate a pulse train when it wants the FET turned on. Pulse train goes away, so does the load. Advantage is that you get to use a great big beefy N-channel FET that costs much less than a little wussy P-channel FET. Add an extra diode and cap if you want to use 12V gate drive (voltage tripler). dwayne -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 22 years of Engineering Innovation (1984 - 2006) .-. .-. .-. .-. .-. .-. .-. .-. .-. .- `-' `-' `-' `-' `-' `-' `-' `-' `-' Do NOT send unsolicited commercial email to this email address. This message neither grants consent to receive unsolicited commercial email nor is intended to solicit commercial email. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist