Isolated high voltage opamp

bitrex · 2015-05-24T19:36:43+00:00

So I have a need for an analog isolation amplifier thing into a HV section at low audio frequencies. I remembered the "HV opamp" thing that John Larkin posted a while back and that seems to work well, but I'd like to isolate the feedback via pwming it and sending it back across the barrier via an optocoupler and integrating. I dont really want to chop it first and have more LV electronics on the HV side than necessary. Instead of having to pick a resistor divider for the largest possible output signal and lose resolution on the PWM I thought I'd bootstrap the PWM IC from the output like so: The components are all just representative and probably not what I'd actually use. It seems like this test circuit should work (the full loop hasn't been closed) but it doesn't appear to sim properly. Any ideas? -- ----Android NewsGroup Reader----

May 24, 2015 21 Replies

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bitrex 11 years ago

No more than about 5khz. The PWM chip takes an input voltage between 0 and 1 volt, so the idea was to float the PWM IC so its rails ride up and down on top of the output voltage and divide the modulation input down from the output, referred to the floating "ground" so as not to lose resolution.

But the LT chip doesn't seem to cooperate with the idea.

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Jim Thompson 11 years ago

I'm not following what you mean. What's the definition of _common_ on the load side ...Jim Thompson

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