# How can I get different voltage inputs from a high voltage power supply?

I want to use a 5 kV DC supply to power a low-current (0.5-3.5 mA) circuit in a microfluidic device.

I would like to create two input voltages from this power supply to have a 300 V drop from 4.3 kV to 4.0 kV across a fluid channel.

I don’t think a voltage divider will work since the load will vary quite a bit during operation. Is there any way I could use voltage regulators for this? The voltage regulators I can find online are not rated anywhere near this type of input voltage. I need the entire channel at high voltage (>3.0 kV) relative to a counter electrode.

• Perhaps use a technique similar to the TL783. (It cannot handle your voltages, but the technique applies.) And there are some opamps that can be powered by the voltage difference of the base to emitter of the very Darlington emitter follower you use to regulate the output, allowing a self-powered opamp for controlling the Darlington. It's not clear to me, but it sounds like you want two regulated outputs from the 5k source? Is that the case?
– jonk
Dec 23, 2021 at 21:37
• Yes you got the right idea, I should have been more clear. I need two regulated outputs. One at 4.3kV and the other at 4kV. Thank you for your help! Dec 23, 2021 at 21:51
• the 4kV output is it a source of current, or a sink? could you use an isolated 300V supply with a resistive divider to keep it at the right potential? Dec 23, 2021 at 22:12
• @MagnusRydberg So, it might be that you'd focus on regulating the 4300 V output and then hanging one or more HV BJT or FET from there to reach down to the 4000 V regulated output. (I'm assuming I'm reading you correctly when you say the loads vary, so they both must be under active regulation where you can't just assume some load.) Or you could do two independent regulators, both feeding from the 5 kV, but using almost identical methods.
– jonk
Dec 23, 2021 at 23:11