No, I'm not talking linux command line utilities, I'm talking mosfets. I'm still not too happy with how the mosfets are switching, in the process of trying to confirm a new power filter, I'v been playing with mosfet drivers. Go figure, it turns out that really big mosfets just dont switch nicely, its not about the gate capacitance to the source, its about the capacitance beween the gate and the drain.

This is a common source amplifer, because of that, its output is inverted. As the gate votlage goes (talking about P channel here) down, the drain voltage goes up, the capacitive coupling between the gate and drain causes the rising output to cancel the efforts of the FET driver, which causes a stall or even reverse of the gate voltage change.

I used moderatly large capacity fets in my design to try to bring down the Rdson, but I think I went too far, there is a point where the fet is so large that its combined capacitances cant be well driven at high frequencies.

My power supply is just 5A, I was playing with some 20V, "75A " fets (much smaller) that were switching much nicer at 250Khz, even at 40Khz you can see a difference.

oh, and with a filter of two stages at 220uH and 47uF I get about 10mv ripple out.

Another side note, you really have to watch were you ground the scope, with switching like this ground voltages stack up fast. If you watch a few episodes of the EEV blog, you will notice him write off the HF chips in his scope readings. most of it really is artifacts from probing the circuit, quantum finish.