Analog Siganl Optocoupling

john wrote in news:8a016f34-1acf-418e-a43a- snipped-for-privacy@a1g2000hsb.googlegroups.com:

Not really

You'd have to let us know some more specs. Such as frequency range, required power level on the isolated side and so on.

Toroid transformers can be an option. AD offers Iso-Amps that have a built in isolated supply for the output buffer. For one-off projects a nice option, else a bit on the pricey side.

The HCNR-200 looks like a nice device. You've got to use negative feedback to make sure that the current coming out of the driven side photodiode matches the signal you are putting in, so the bandwidth that you can get is limited - as the other responses have mentioned, we need to know this to be able to give you useful advice.

A differential amplifier (or an instrumentation amplifier, which can often do better) doesn't allow you to separate your ground systems, but it can allow you to reference your signal to the "ground" voltage in the area where you plan to use the signal, which may well be different from the "ground" voltage you'd measure on the National Instruments DAC board (6071E).

I've not used this device, but it looks as if this capability might already be built into the DAC board.

Such amplifiers have finite bandwidths and you might want to add a balancing transformer (balun) to handle higher frequency voltage differences.

-- Bill Sloman, Nijmegen

Hi,

Why an opamp's virtual gorund can not be a good electrical isolation system?

john

It _can_ be reasonably useful, provided the ground potential differences are small (and not really high frequency).

Put pencil to paper with input, Vin, relative to ground, VG1, and output, Vout, relative to ground, VG2.

Then examine possible dynamic range and frequency issues.

You will find that you will learn a lot more, if you do your own math, than you will from just blindly asking questions.

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

First you have to define what you mean by isolation. How many volts? What frequency range does the isolation have to work for? How many dB of isolation?

Except for low level audio work a virtual ground usually doesn't work well. Not many volts and slouches off at higher frequencies.

john wrote in news:9b16eae3-fec5-45d0-ae69- snipped-for-privacy@l42g2000hsc.googlegroups.com:

Saturate your op amp, and what happens??