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Opto coupler CTR curve

Discussion in 'Electronic Design' started by Engin Ciftci, Dec 22, 2006.

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  1. Engin Ciftci

    Engin Ciftci Guest

    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
     
  2. Jim Thompson

    Jim Thompson Guest

    Can you afford an HCNR201 (a matched pair)?

    ...Jim Thompson
     
  3. Genome

    Genome Guest

    You mean

    http://www.fairchildsemi.com/ds/H1/H11AA1.pdf

    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
     
  4. 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


    When I mean digital opto , I mean it has 2 states off or on.
     
  5. Engin Ciftci

    Engin Ciftci Guest

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

    Jim Thompson yazdi:
     
  6. Engin Ciftci

    Engin Ciftci Guest

    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:
     
  7. John Fields

    John Fields Guest

     
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