[time-nuts] fast edge, rise time.

[ct1dmk]

Hello,

I'm willing to generate a pulse (of some few hundred volts)
by discharging a capacitor into a pulse transformer
I'm solely interested is the active edge (call it either rise or fall 
depending on the
wiring of the output of the transformer).

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 would be happy to receive some comments/ideas that may pop out of your 
heads.
Thanks.

hope that my quest for fast rise "time" is not too off topic on this 
"time" list...
but... there are so many experts on this list that I could not resist ;-)

Luis Cupido
ct1dmk.


p.s. ( I switch a capacitor to GND with a transistor (fet or bipolar). 
that capacitor has a charging resistor to 48V, transformer has a 9:1 
voltage ratio. Pulse average power is quite low a few watt only. At the 
primary side some 20A of peak current for less than 100ns... and very 
low duty cycle. )