ok I ordered fet drivers, I'm testing, please stand by.

Jan 7/2016

--

So it turns out that a 555 is a GREAT fet driver IF you have the input levels at EXACTLY the right bias and amplitude, slightly off and the duty of the signal your driving goes really, really wrong. so I bought some official fet drivers. IRF4427.

I'v recieved the drivers and they seem to drive the fets ok, as good as, or a little better than the 555 was.

One of the other problems thats come up since I breadboarded this circuit is that there is a 0.2us, 5Mhz, .02V 'ring' in the ramp signal where it crosses the threshold votlage of the control signal. For the most part this dosn't cause a problem, untill the control voltage is close to the peaks of the ramp, at which point it causes a brief glitch in the pwm comparitor output, which is then amplified by all the stages and comes out quite clearly on the output of the fet driver.

I'm looking at two methods of fixing this,

a) drop 1.4V off the comparitor output. The spike, at the output of the pwm comparitor, is only about 0.7V, much less than the 5V of the rest of the pwm signal.

b) new ramp oscillator circuit.... again? really?

welcome to 2016 everyone!