Hi all,
I want to build a curve tracer front-end for an oscilloscope and would like to use a voltage amplifier for the collector sweep voltage. (The goal is to also be able to profile tubes--so, also plate voltage.) The transformer I'll use gives me +/- 450V. I found this circuit on the net and it would be pretty much exactly what I have in mind. (The PDF is also attached at the end.)

There are some fairly obvious errors in this schematic such as the top and bottom MOSFETs not being connected to power and I think there's a missing connection at R24, 25, 26, 27. Also, the connection in the feedback at Q11, R23 shouldn't be there(?). Anyway, I've simulated this in LTSpice using FQP3P50 (P) and FQP3N80C (N) MOSFETs and can't get it to work. I'm no circuit analyst, true, but this looks kinda strange. And this may be kind of overkill anyway.
Does anyone know of a circuit that would work or maybe what else is wrong with the pictured circuit? The supply probably doesn't have to go + and - as long as I can swap polarity (though that would be nice).
Thanks for reading,
Michael (aka Totoro)
high-voltage amp circuit.pdf (119.87 kB - downloaded 58 times.)