Tony.G wrote:
.....
 So I decided to
>spend a few extra dollars and use the P/N combination in that circuit. And
>yes, I've been making sure that I hook them up right, with the correct FETs
>in the correct places.


Hmmm, from the description of your problem, it sounded like you could
possibly have had the source and drain terminals reversed on the upper
p-channel devices.
==========

>
>On your page (very useful page, BTW!), at "H-Bridge Theory[1]" is this page
>and schematic:
>http://www.cadvision.com/blanchas/hexfet/
>http://www.cadvision.com/blanchas/hexfet/np-s.pdf
>
>That's just about exactly what my circuit is now as far as connections (part
>#'s are different), except for the status LED's and the diodes.


You will notice on this schematic he shows the drains connected together,
and the souces tied to gnd and Vcc. Some schematics around have the p-chan
drain to Vcc - which I think is wrong.
============


.......
 Some of the
>pages I've read concerning H-bridges have said that you should use the
>supression diodes when switching with transistors, but that many MOSFET's
>have the diodes built in and external ones are unnecessary. Should I go ahead
>and drop some of these in, at least to play it safe?
>

This was discussed just last month on piclist - take a look at the
following thread:

[EE]: IRL540 MOSFET Question
http://www.infosite.com/~jkeyzer/piclist/2001/Jul/1392.html


- dan
========

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