Dale Botkin wrote...

>On Wed, 20 Feb 2002, Dave Dilatush wrote:
>
>> The circuit DOES work, and the MOSFET body diodes do NOT conduct.
>
>Cool.  I understand now.  Neat idea, I think I'll kick this project up a
>couple of notches on the list!  Time to order more parts...  8-)

The IRLZ44N's that Speff suggested would be good candidates.  The lower
the Rds(on) the better.

>> I have two IRF512's connected to a 12V transformer and a light bulb
>> running on the workbench right now; the circuit gives full-wave ON/OFF
>> control (I can turn it on and off just by touching the gates with my
>> fingertip... neat!), with no current other than leakage flowing when =
OFF
>> and no voltage drop when on, other than that due to Rds(on).
>
>So am I correct in thinking that turning on just one of the gates will =
run
>the lamp at about half intensity, while the other MOSFET gets warm?

Yup.  Just tried it.  Though "warm" in the case of the setup I have
running is kinda theoretical, as I'm only driving a 250 mA bulb and the
=46ET is in a TO-220 package.  But if I put my scope across drain and
source of the "off" MOSFET, I can see the drop across its body diode
when the other MOSFET is conducting.  So it appears to be doing what you
said.

The more I fool around with this circuit, the stranger it gets.  What we
have here is a "Logic Controlled Diode" with two control inputs:

  0 0 =3D doesn't pass any current
  0 1 =3D passes current to the right
  1 0 =3D passes current to the left
  1 1 =3D passes current both ways

Wonder what applications there might be for such a thing?  Hmmm...

>> * FAD =3D Field-Assisted Diode  :)
>
>I just try to avoid NEDs -- Noise Emitting Diodes (SNAP!!)

There are also DEDs- which is what you get when you put exactly the
right amount of current into an LED to change the doping levels and
crystal structure so that it emits darkness instead of light.

Technically, at the LED/DED Transition Point the device is said to be
"on its last GaAsP"...

Cheers,

Dave

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