[time-nuts] fast edge, rise time.

[Al Wolfe]

Years ago I had a cousin who ran a civilian calibration lab. For calibrating 
scopes, etc, for rise time he used a mercury wetted relay which he claimed 
had nearly instant rise time and no bounce. Seems that he used a resistive 
divider and the mercury relay shunted a portion of the divider. With very 
small inductances and capacitance to slow things down it would seem to be 
very fast.

Al, k9si, retired



> 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.
>