> I just pulled an old text from the shelf, and it clearly explains how IN
> THEORY, MOSFET's, both N & P channel will work with either positive or
> negative gate bias.

No arguments here :-)

I mentioned enhancement and depletion mode FETs and that the overwhelmingly
most common form is enhancement mode. This means that they are OFF until
ENHANCED on. A depletion mode FET is on until DEPLETED off. This will all be
covered in the text books. If we are dealing with real world devices then we
have to run with what they make.

Also note that IF you could reasonably make an N Channel MOSFET which
operated with either positive or negative gate bias relative to the source
and IF it was about as good as existing real N Channel FETS then it would
seeep away almost all P Channel FET applications (as it does what they do as
well) and probably replace most N FET designs as well.  I'd buy them :-).

> Well, Russ, I guess you didn't write all the books...

Indeed. But I read all the data sheets that I can get hold of :-)

What people make and sell is the ultimate arbiter (alas) of what you have to
do to make them work. Current MOSFETS are sold as 2 quadrant devices at
present (ie gate with one polarity, drain with either) and the 2nd quadrant
is not overly useful in most cases due to the body diode.



            Russell McMahon

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