RE: An extremely good MOSFET driver

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

Original poster: "Mccauley, Daniel H by way of Terry Fritz <twftesla-at-qwest-dot-net>" <daniel.h.mccauley-at-lmco-dot-com>

> This circuit shown below:
> 
> http://www.spacecatlighting-dot-com/datasheets/mosfetdriver.pdf
> 
> is an extremely fast mosfet driver circuit...

[snipped]

Whoa!...I took a closer look:  Dan, am I missing something or do I see a
problem with Q6?  Each time the transformer-secondary voltage becomes -
on top & + on the bottom, does not Q6's base:collector junction become
forward biased?  That's going to ruin the other secondary's output, when
it's (presumably) trying to turn on its MOSFET.

Hmmm...

No.  When the gate transformer is "positive", Q5 turns on and Q1 get
"slammed" on.  At this time, C28 also
charges up.  When the gate transformer goes "negative", Q5 turns off, Q6
turns on and with the help of C28, allows
the gate capacitance of Q1 to discharge very fast and thereby turning off Q1
very fast.  

Dan

When working on a prototype version of my SSTC#1, I used this circuit in a
half-bridge and got almost perfectly square (rise / fall times < 100nS) gate
drive waveforms up to about 450kHz. However, this circuit does dissipate a
bit of heat - thats for sure.

Dan