[time-nuts] fast edge, rise time.

Bob Camp lists at rtty.us
Thu Dec 26 21:26:51 EST 2013


Hi

Unless you want run for < 1 second, that rules out a Krytron. 

Length of operation also impacts some of the other implementations. 

Bob

On Dec 26, 2013, at 9:16 PM, ct1dmk <ct1dmk at gmail.com> wrote:

> Many thanks to all for the nice tips.
> 
> I may narrow down by saying a few more specs as suggested.
> The pulse would see a somehow unknown load but for a start I
> was suggested to have my source with 50ohm impedance so worst
> case would be a short circuit and therefore the pulse would be a current pulse
> and would have some 10Amp. Pulse length about 100ns so only some 0.5mJ energy that would die inside the pulse source( this would be the worst case).
> The 100us repetition rate make a a very small duty cycle of 1/1000 so average power
> maximum 5W.
> 
> Since the amplitude and timing parameters are to be controlled (pulse timing come from an FPGA) I really need a solution using that trivial switching element fet or bipolar (and can't really do a more exotic scheme if I cant electronically control the parameters) also I must use a transformer because these short pulse are to be superimposed to another voltage and a transformer becomes very handy to do that. I interrupt the wire and insert the secondary there to add the pulses.
> 
> The challenge I'm facing is on the device either RF FET or Biplolar tr etc. and
> surrounding circuits, transformer, etc. this to achieve the 4ns (or 5ns).
> (the transformer I have in mind is something very similar to those transformers
> on the final stages of HF/VHF ham radio amps, coax cables and ferrite cores)
> any suggestion regarding devices etc ?...
> 
> Thanks for all comments.
> 
> Luis Cupido.
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