[sci.electronics] Looking for fast high voltage op amp

msd@enh.nist.gov (M. Scott Dewey) (01/09/91)

Greetings!

We are trying to build what amounts to a fast high voltage op amp.  This
device will be used to drive a small penning trap electrode (a 50 picofarad
capacitive load) between 0 and 900 volts.  In order to minimize the loss of
trapped particles during the voltage swing, we'd like the rise and fall
time of this device to be less than 10 microseconds.  Input for the device
will be two low level voltages (each one between 0 and 10 volts) and a TTL
signal to switch the output between the two input states.  Evidently the
gain of the device will be of order 900/9 = 100.

We've tried building a circuit that features both an op amp driving a high
voltage transister and several filter capacitors, but we've not succeeded
in getting a stable beast with a rise and fall time of 10 microseconds yet.
None of us is an electronics expert.  Is anyone aware of an item of
commerce that would do what we want?  Does anyone have a schematic that
they'd be willing to share?

Thanks!
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