I don't know what you mean by overdriving... If you exceed maximum Vgs, I don't think you could gain any speed.
Let's consider Ixys
**broken link removed**. Data sheet states
td(on)=15ns(typ.) Conditions under which was tested are 20\[\Omega\] gate resistor and 10V pulse to achieve current of 3.6A (
Id25)
When you take into account gate capacitance, what Vgs is required to get to those 3.6A, you will come close to those 15ns. Now if your circuit is well done and you dont have undesired oscillations, you can bypass resistor with capacitor creating RLC circuit with lead inductance, gate capacitance lead resistance... You want to tune gate circuit but first you have to make sure layout, decoupling and everything else is way it should be. You have to treat design as dealing with RF. Once you achieve that Vgs rises much faster than desired 10ns, you will see what kind of performance you could squeeze out of that transistor.
As for 400W, you should be concerned with maximum energy rating of transistor. 400W you talk about should be supplied by decoupling capacitors, not the PSU.(given that frequency of the pulses does not have to be to high)
Just to add, if you want to achieve really fast, HV pulses, BJT in avalanche mode could give you sub ns pulses. You have to be aware that whole signal path from source to the load has to perform at those frequencies.
My opinion is that you can't change input before output is changed, so you have to wait for the propagation time. Then the minimum period will be the sum of propagation times.
This seems more similar to what I remember. Think at 74HC CMOS logic. Typical transition times at Vcc = 5 V are around 5 ns this means maximum frequency of 100 MHz.
Typical propagation times are more than 10 ns, if I'm right this lead to maximum frequency of less than 50 MHz. More realistic
Consider 50 inverter gates connected in series. Is maximum frequency you could run through those gates 1/(
tp*50)?