[time-nuts] fast edge, rise time.

[Marek Peca]

> The target is 4ns, while ideas seemed to be clear at some point, now I'm
> having doubts if better to use a MOSFET or a bipolar transistor
> as the switch element. Experiments with MOSFETs presented me some 
> difficulties charging the gate capacitance having some trouble to achieve 
> something in the 4ns region. Well 4ns seems hard whatever device anyway.

I have seen recently two kinds of devices for similar task: MOSFETs and 
avalanche breakdown transistors. Try the second ones, might be a good fit 
if the pulsing is not very frequent (say, kHz range).

Regards,
Marek