Dear zlymex thanks for sharing your time and knowledge with us, I have some basic questions regarding your bootstrap circuit.
First of all can I power your circuit with +1100V and -1100V power supply so that I could measure AC voltages?
2- what is the purpose of Q1-Q4? I think they are acting like normal diodes, why didn’t you use a normal diode instead?
3-what are R6-R9 doing in your circuit? Doesn’t they generate some voltage drop for us, because we should connect the output of this circuit to the 10Mohm voltage divider, also for current limitation you have used Q5,Q6 as a J-FET can we replace them with simple BJT or MOSFET.
4- why did you use R1-R5 in series with the op-amp? What are they doing?
5- you mentioned the input should be 50V-1000V, so what happens to lower input voltages? For example, the mV and uV input voltages? Also what would affect the circuit performance, I mean which part are critical for achieving the Best lowest temp co-efficient?
Thanks in advance