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Opto coupler CTR curve

In most of the opto-coupler data sheets min CTR value is given. But there is no comment on max value and the typical value for the CTR value. I have measured different parts in different parties for the same opto-coupler (H11AA1) and saw that they are surprisingly varied. Also their actual CTR values are far from the min CTR value given in the data sheet.

So i gave up finding a low cost opto-coupler with a constant or limited CTR value. My question is:

How can I fix or compensate CTR variations in my circuits. I have tried many combinations of feedback circuits and they not satisfactory to fulfill my expectations. One constraint in my design is I can not add additional component such as capacitor or a series resistor to cancel pole of the current transfer function.

Any suggestions?

Thanks a lot.

Engin

Reply to
Engin Ciftci
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Can you afford an HCNR201 (a matched pair)?

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.
Reply to
Jim Thompson

You mean

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My Landlord and 'friends' went to Turkey for a holiday. Full board in the Hotel.

Turns out the food was shit and they played seriously loud music all the time. Result was my Landlord and 'friends' were forced to 'eat out' in places provided by the hotel owners family.

I guess that means it is payback time.

Your situation on this subject is?

And.... you are using an AC optocoupler in its linear region for why?

'One constraint in my design is I can not add additional component such as capacitor or a series resistor to cancel pole of the current transfer function.'

I'll assume you know what you are on about and suggest that 'the management' needs a good kicking for not allowing you to do that.

DNA

Reply to
Genome

The H11AA1 is designed as a digital opto coupler (not analogue linear) hence your design should cater for the min CTR (IE the worst case).

If you need to pass a linear signal over the opto - then use something else.

So you have found variations in the CTR.. ALsO the LED age and the CTR may vary over time.

So use a specific linear opto or something else.

JG

Reply to
Joe G (Home)

I will contact to check for the prices. Thank you for your suggestion.

Jim Thompson yazdi:

Reply to
Engin Ciftci

First of all I'm sorry that your friends have a bad experience on holiday. Many travel companies are mostly interested with your money and they forgot that they are wasting your invaluable time.

My situation is: There is a board that was previously designed. I am trying to lower the cost of board by trowing out some components which are problem in production.

I am using optocoupler in linear region because I need to extract mainly a monotone signal which is added on a dc value.

Actually I don't care if the waveform of the sinusoidal signal is deformed because of nonlinearities. I use a filter to get the fundamental freq.

Genome yazdi:

Reply to
Engin Ciftci 

--
If you need the galvanic isolation, use a cheap transformer that can
handle the LED current without saturating.  If you don\'t, just
replace the optocoupler with a capacitor.  And please don\'t top
post.
Reply to
John Fields

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