Re: An extremely good MOSFET driver

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

Original poster: "K. C. Herrick by way of Terry Fritz <twftesla-at-qwest-dot-net>" <kchdlh-at-juno-dot-com>

On Wed, 07 Aug 2002 17:06:03 -0600 "Tesla list" <tesla-at-pupman-dot-com>
writes:
> Original poster: "Malcolm Watts by way of Terry Fritz 
> <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>
> 
> HI Ken,
>         The [
http://www.spacecatlighting-dot-com/datasheets/mosfetdriver.pdf ] drive
scheme is very often used because:

[snipped]
 
> the bases are tied together as are the emitters. It is not possible 
> 
> for both transistors to conduct simultaneously. While it works 
> extremely well, it does mean that there is something of a high 
> impedance connection to the power device drive element while the 
> driver is transitioning between its power rails. Not a perfect 
> situation.
> 
> Regards,
> malcolm

Malcolm (& all)-

Right...as to the spacecatlighting circuit that I think you are referring
to.  But I was referring to a pair of power MOSFETs that that circuit
probably drives, in a half-bridge configuration.  For those transistors,
both must never be on at the same time, even for an instant.  Such an
instant is when one is turning on & the other, off.  That's when you need
to turn the one >on< relatively slowly while the other is turning >off<
as fast as you can get it to do so.

Ken Herrick