[time-nuts] Isolation achieved by opamp based isoamp?

J. Forster jfor at quikus.com
Thu Nov 21 09:28:49 EST 2013


Looking quickly at the prints on the site, the isolation is provided by
the transformer, not the active circuitry. The transistors/op-amps are
just buffers for the output.

That means that the isolation is determined, for the most part, by the
transformer design, so:

 A bifilar wound torroid would have relatively poor isolation,
 Two windings on opposite ends of a ferrite rod much better.

Some (power line) ultra-isolation transformers have a shield between the
primary and secondary, and I don't see any reason that could not be done
at RF. The objective is, of course, to minimize the capacitance between
the windings. Topaz got 0.001 pF on a 1 kW unit as I remember.

-John

=================






> Hi,
>
> I'm curious about the level of isolation that is achieved by an opamp
> based
> isoamp. I'm referring to ones described here on Bruce Griffiths' page:
> http://www.ko4bb.com/~bruce/IsolationAmplifiers.html
>
> Anyone has a number for this?
>
> I've tried googling it, but the results are mostly filled with the other
> kind of iso amplifier where isolation refers to galvanic isolation.
>
> Regards,
>
> Stephan.
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