Re: Adapting An Electrophoresis HVDC Power Supply To Microampere Level

SMH wrote:

I had posted this problem earlier, but without detailing much how the power supply is to be used.

I have written a perhaps more detailed web page that explains how it is to be used.

I put this question to a professor of electrical engineering who is an expert in circuit design, but he could not give much time to it and wrote a schematic that was short of what I needed, such as which parts to buy (name and/or part number) so that I can build something to test. I put his explanation and drawn schematic on this web page. If someone can actually name the part numbers, I can buy and put them together for testing (if you can suggest where I buy them too, that would be helpful).

http://tinyurl.com/3yxzev

I was looking for a low cost (say no more than a couple of hundred dollars), easily implementable solution.

That solution could be buying an already assembled set of components in the box from a maker, or building something on a circuit (prototype?) board with components piece-by-piece...opamp, MOSFET, resistor, capacitor, etc.

It must be a solution that requires that the person has only a fundamental understanding of the physics of electricity, and who may know how to use a soldering iron.
In theory, that circuit will work, except (as previously noted) the FET will not be able to withstand more than 1000V.
Granted that a number of FETs can be daisy-chained (or cascoded), but that can be risky.
Why not start with an AC to DC supply where the level of the DC is continuously adjustable from zero to full value by adjusting the AC input?
Now a FWB in series with the AC input can allow the DC equivalent of a variable resistor to be used for that adjusting, and the maximum voltage (120VAC line) could allow a FET with a 400V rating act as that variable resistor.
Does that sound like a step in the right direction?
If so, someone here could design and make a number of these beasties...
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