I was inspired to do some learning by the audio driver project recently discussed.
"Board for WA1GFZ MOSFET Audio Driver"
http://amfone.net/Amforum/index.php?topic=44619.0It's interesting to learn about analog/linear use of MOSFETs at high voltages and moderate currents. What I have been thinking about is not for grid drive but more to appreciate what can be accomplished with higher voltages than usual. The bottom line is that with the FET, only a few parts are needed compared to bipolar transistors. Just like good ole tubes. The project inspired me to try a few things in LTspice.
Messed around with slightly different FETs, resistor values, etc. cranked the virtual supplies to +/-500V and changed biasing to suit the operating points, and put together in there a series arrangement of MOSFETs for the higher voltage. At the higher supply voltages, LTspice showed 400V peak to peak voltage @1A peak 'grid' current on the positive half cycle. I make no claims about it in real life and high current would mean large heatsinks. I can only offer caveats at 1KV with transistors.
Just for fun here is the series MOSFET follower circuit that looks good for higher voltage than one device alone could handle with a safety margin.
When substituted for one output device in the +/-500V simulation based on the driver article, it performed like the single part, with margin to spare for the higher voltage. The drive from one side of the phase splitter was just over 400V p-p, so that's all this was simulated with today, but it should be able to get closer to the rails if driven harder, carefully biased, and everything is perfect, which it never is.
This has little to do with the original product's purpose, but might be useful where higher dynamic and variable voltages are wanted for ham radio purposes. It's based on ideas from many published circuits. There's no 'protection' on it so beware the real-life experiments. FETs are always cheap in LTspice.
Can several MOSFETs be stacked next to a resistive voltage divider and serve as one very high voltage part? why not. Last time I saw that kind of thing in real life was as a regulator in a 2200V current limited power supply. It had a row of very expensive Darlington transistors in there. FETs didn't exist then.