Isolated high voltage opamp

What is HV ? 1000 Vac/1500 Vdc according to IEC or something else ?

What is low audio frequency ? 20 Hz, 100 Hz or 300 hz (telephony) ?

On Sun, 24 May 2015 15:36:43 -0400 (EDT), bitrex wrote:

I tweaked the basic HV opamp circuit a little...

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which seems to make the output waveform a little cleaner.

That LT1024 is a little wussy for this application, in my opinion.

I didn't understand the PWM thing, and it really slows the sim, so I ripped it out.

Looks good but I guess we need to know how much isolation he needs. Yours is 1Meg out-to-in, yes? Also, the 1Meg has a voltage limit as discussed in another thread.

Have I overlooked something?

On Mon, 25 May 2015 08:14:15 -0500, John S Gave us:

Yes. You are missing about 40 trillion functional neurons...

Try researching what the highest isolation voltage available in an opto-isolator is.

AlwaysWrong reports his own experience, more or less correctly by his own standards - he's actually got a few more neurones than two, but not nearly enough.

On Mon, 25 May 2015 06:50:53 -0700 (PDT), Bill Sloman Gave us:

Says the 'maroon' who cannot even spell the word 'neurons' correctly. I'll bet you say "idear" as well.

At the moment the +150 -150 volts is sufficient, but I was also interested in developing a topology that would work for significantly higher voltages...like a thousand or more plus to minus. I don't think a resistor from output to input would be appropriate in that case. Hence the PWM idea.

Can you tell us how much isolation you need? A 1T ohm resistor can provide 1T ohm of isolation, of course. And JL has some, so they are available. Need to know more.

e:

You'd be wrong. If you weren't AlwaysWrong, you'd be aware that "neuron" is one of the mistakes Noah Webster wished on the gullible American public in his scheme to make Americans spell English in a way that wasn't documented in the English language dictionaries published in the UK.

He foisted his dictionary on the American public, and you are still sufferi ng from his commercial acumen and total lack of linguistic principle.

I speak and write English English - which isn't wildly different from the A ustralian English that I learnt as child - and spent 22 years working in th e UK, so I write "neurone". I understand what Americans mean when they writ e "neuron" but I don't bother spelling the word the way they do.

Watch for the Apex PA99, coming soon... 2500V total supply... I begin behavioral modeling it the first week of June. ...Jim Thompson

Fairchild's MOC207 is rated at 70V, whereas their MOC8204 is rated at 400V. The CTR is much lower. Watch out for the class-A current * 400 volts.

The ones we drew aren't isolated at all; the power supplies are all grounded.

I guess the idea of the deleted PWM box is to measure some voltage and opto-couple it back to the grounded side, which would allow shuffling grounds to give full isolation. I'm not sure.

Unless you plan to float the +-HV supplies, to get true isolation, a feedback sense resistor will work fine. 100 Meg, 1 G, something like that.

Powering a PWM circuit from kilovolt supplies will be inefficient.

To push my circuit past the voltage rating of the MOC8204s, you can cascode better, low voltage optocouplers into depletion fets.

Or use photovoltaic optocouplers into conventional high voltage mosfets. Easy but slow.

That's my original circuit, from 2005 I think.

I used it to bias the collection electrodes in a 2D delay-line detector, behind a microchannel plate. Didn't make any money, but it was fun.

That ought to work for bitrex. ...Jim Thompson

Since Spice usually ignores breakdown voltages, you may as well simulate with some part that's in the standard library.

John Larkin Wrote in message:

Correct

Yes, that should. I was experimenting with also isolating the feedback loop with PWM and an optocoupler for total galvanic isolation, but cannot seem to pull it off.

What's the frequency of your signal? If it's essentially DC, PWM should be relatively easy... ramp and dump? ...Jim Thompson