I want to use this TRANS NPN 700V 3A TO-220 (https://www.icrfq.com/part/1915575-BUL7216.html) transistors on my electrostatic machine. Is there any problem if the HV capacitor at the base of the transistor has about the same capacitance?
Your problem will be that a static machine gives of much more than 700 volts.
Do you want to couple the base at high voltage ?? Give a schematic.
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I think i know what your after but your playing a risky game and you need to cascade a number of mos fets to do it you will need a number of support components as well to make it work and protect the mos fets.