That was the biggest problem, I remember them having 1 - 2us rise/fall times which is far too slow, when I found the fast ones I couldnt get them and the voltages were a little low. What I'm doing is driving an IGBT, I have seen many people drive them directly with a transformer but I find voltage spikes quickly kill them. So I thought of using the transformer to drive a comparator to then drive a IGBT driver chip which drives the IGBT. Im having a lot of trouble with the signal from the transformer driving anything. I think my problem may be that I have too many turns on the transformer and at these speeds 50-100kHz the impedance is too high and therefore not enough current coming form the secondary. What do you think?