[time-nuts] fast edge, rise time.

[Gerhard Hoffmann]

Am 26.12.2013 17:07, schrieb 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. )

We once built an ultrasonic pipeline pig with 1024 transmit/receive 
channels,
so everything had to be quite compact. The transmitting parts of the 
transducers
were hit with 350V pulses with a few ns risetime and 50 Ohm source impedance
and they rang on their favourite frequency. No transformer at all.

We used avalanche transistors to produce the pulses, a small smd bipolar
made by Zetex (afaik that's now bought up by Diodes, inc). Old 2N3904 are
said to avalanche also quite good.

The drawback is the repetition rate.

Doing it as a 'normal' amplifier w/o transformer will require a cascode 
stage
but should work also.

But then I think you know that already since I've seen your presentation
of the TWT switcher PS on the EME meeting in Paris  15?? years ago. :-)

73, Gerhard