On Wed, 20 Feb 2002, Dwayne Reid wrote:

> Dale - this will work just fine.  I've used it before.
>
> Remember that a conducting MOSFET looks like a resistor, NOT a saturated
> bipolar transistor.  As such, it conducts BOTH directions when enhanced
> (on).  In other words, the Vf of the body diode is swamped by the ON
> resistance of the FET.  Because Dave drives both gates at the same time,
> both FETs are turned on.
>

  Well, what you probably forgot Dwaine, ( even if this circuit is
probably working ) is the ideea that conducting MOSFET looks like a
resistor,ONLY for small Vdrain-source voltage. I have not see any diode on
this drawing from drain to source, so I believed it not works.
  However, two transistors for just driving a bulb is too much !
The problem was already solved more than 10 years ago ( in the same way
like magnetron filament current limiting inside any domestic oven ) by
using a simple high loose magnetic core suply transformer. Than a simple
scr or relay is solving the problem. No pic ( pwm, zero cross detection
and so on) is required for this.
Transforming a standard 110 or 220/12V ac transformer into a high loose
one or computing a new one is an easy task ( not working on toroidal
core... )

best regards, Vasile

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