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Author Topic: Look for Analog isolation  (Read 2244 times)
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nanocycle
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« on: April 25, 2010, 06:16:23 18:16 »

Hi guys  Wink

In a circuit i need to isolate analog signal from the rest of parts.


what is your suggestion.

Regards,
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solutions
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« Reply #1 on: April 25, 2010, 08:48:31 20:48 »

Need more info about nature of signal and barrier.  Like all design engineering choices there need to be constraints and requirements specified.

Among these:

1) frequency
2) DC content desired or not?
3) Is there a DC component that needs to go across the isolation barrier
4) Isolation voltage
5) magnitude (amplitude) and dynamic range
6) distortion requirements
7) available power on both sides or is it powered by the isolation mechanism

etc
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samir
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« Reply #2 on: April 29, 2010, 06:50:58 06:50 »

Hi
If you want ac signal(50Hz to 22Khz),you can simply use transformer as used in Audio power amp.
For Dc signal you can use ISO121 if price is not concern.
http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?family=analog&familyId=512&uiTemplateId=NODE_STRY_PGE_T&paramCriteria=no

One more solution use Serial DAC with Opto coupler at input so it can be isolated.
Third solution Use V To F converter,isolate Digitat signal using opt and than use F to V converter at another side.
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kalpakchiev
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« Reply #3 on: April 29, 2010, 06:59:04 06:59 »

It  is hard to answer the question asked by Nanocycle, before having information which is mentioned by Solutions.

Best regards
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A known mistake is better than an unknown truth.
microkid
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« Reply #4 on: April 29, 2010, 03:01:19 15:01 »

HCNR 200
TIL300
are some of the linear optocouplers which i got while googling

For more parts google with linear optocouplers and linear optoisolators

MicroKid
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DreamCat
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« Reply #5 on: April 30, 2010, 06:34:17 06:34 »

transformer

optocoupler only can use in dc signal.
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May be I expressed the wrong meaning, sorry for my bad english. Please correct it for me if you can.
sputnik
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« Reply #6 on: April 30, 2010, 06:40:20 06:40 »

transformer

optocoupler only can use in dc signal.

There are optocouplers that will work with A/C. They have 2 led's (bi-directional), however I do not know how linear they are.
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solutions
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« Reply #7 on: April 30, 2010, 06:52:09 06:52 »

transformer

optocoupler only can use in dc signal.
...and transformer can't pass DC

Impossible to solve the problem if you don't know the problem.  Does the 220V 50 Hz have a size/weight constraint?  Reliability requirement?  Failsafe?

As you can see, all you get is GUESSES

FWIW, CATV is analog RF (AC) on fiber...OPTO

Since you have a diode detector downstream AND an attenuator in your original posting, I'd say an LED+resistor and a photodiode/transistor type of optoisolator will do what you want quite nicely as it eliminates a lot of your downstream components that you've shown.
« Last Edit: April 30, 2010, 07:01:53 07:01 by solutions » Logged
petarp
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« Reply #8 on: April 30, 2010, 06:55:17 18:55 »

Hi. Loook at HCPL7840 from AVAGO/Agilent.

http://www.avagotech.com/pages/en/optocouplers_plastic/plastic_miniature_isolation_amplifier/hcpl-7840/

Best Regars.
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Jehan
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« Reply #9 on: June 24, 2010, 04:02:00 16:02 »

check www.nve.com  GMR based analog and digital couplers
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masa
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« Reply #10 on: August 08, 2010, 02:09:28 02:09 »

there's isolation amps, ad202/ad204
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