Re: A prospective MOSFET driver

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Dave,

On 6 Aug 2002, at 22:04, Tesla list wrote:

> Original poster: "David Sharpe by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <sccr4us-at-erols-dot-com>
> 
> Ken
> I see what you're trying to accomplish.  My only comment is
> when you are biasing Q2 on via the pulse transformer via D1
> with a positive polarity (and of course biasing Q1 off at the
> same time).
> 
> I've always been told to NEVER forward bias a zener diode,
> you will hose its knee characteristics.  Comments from the
> list???

Interesting. I haven't heard that before (gulp!). I haven't seen 
degradation in zeners I've forward biased but the current was pretty 
modest and zeners are not noted for their current handling 
capability. In fact, I think you've hit on a severe drawback to the 
circuit right there! I never thought about it. The peak gate current 
could be in the Amps range.

Regards,
malcolm

> Regards
> Dave Sharpe, TCBOR
> Chesterfield, VA USA
> 
> Tesla list wrote:
> 
> > Original poster: "K. C. Herrick by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <kchdlh-at-juno-dot-com>
> >
> > Would MOSFET-literate coilers care to comment on a prospective driver
> > circuit?  See TCH-DRVR.gif at http://hot-streamer-dot-com/temp  I've not
> > tried it but it seems reasonable.  The main purpose is to turn the power
> > MOSFET (Q2) on slowly ond off fast--for the case of a "totem pole" or
> > similar circuit.
> >
> > http://hot-streamer-dot-com/temp/TCH-DRVR.gif
> >
> > Ken Herrick
> 
> 
> 
>