HV current mirror

Hello, I need to create a high voltage, extremely accurate current mirror. I tried to make this circuit with analog circuitry and opamps but I get oscillations that I can not manage to quell and I don’t feel too comfortable floating a 16v opamp up to near 200v to act as a high side current mirror either, at least not as a long term solution.

This is what I had in mind.

Basically the M2 circuit is doing its own thing and I need M1 to replicate the DC current conditions of M2 as accurately as possible.
How accurate? Well the opamp I was using is accurate down to 1uv. This is even more an issue now that I’m using the feedback device on the low-side instead of high-side like I was before so now I have the accuracy of R6 7 8 and 9 to deal with.

Actually on that topic, I was wondering if some sort of auto calibration could be done to eliminate the error of those resistors. Even a small misreading will generate significant DC error at M1, even without those voltage dropping resistors in the way.

How feasible is this and what would be required?

Thanks in advance, I really need this circuit to work.

Anyone? I'm at least looking for a basic outline of what I would need to get it to work.

No one?

You might be better off asking in an electronics engineering forum rather than an Arduino forum. Sorry.

I don’t know how much current is involved, but the enclosed would do it for small values.

The accuracy depends on the matching of R1 and R2 - 1k would be ok for a few mA

The second circuit is a conventional Wilson current mirror - to be accurate it needs matched transistors and close thermal coupling. It’s accuracy can be improved with resistors in each of the emitters connected to HT.

Allan.

Isrc.pdf (20.6 KB)

Isrc2.pdf (14.7 KB)