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Photodiode current limiting/attenuating IC or solution

Jayaram C B
Intellectual 370 points

Other Parts Discussed in Thread: LOG112

We have an application wherein a photodiode is interfaced with Log112 and the reference current used by us is 1mA(by using 2.5K ohm resistor with 2.5V inbuilt reference of Log112). Under certain conditions, the photodiode current is going beyond 1mA(it goes to 15mA to 20mA in some cases). Is there any IC(or any other solution) available in Texas instruments product range which shall have current attenuation feature whereby the photodiode current can be attenuated before routing to Log112. Pl let me know.

 

Thanks in advance for your time.

 

Regards,

Jayaram C B

  • 0
    Guru 21975 points

    Jayaram,

    If I understand correctly, you want to attenuate the input current by a constant linear factor. Is that correct?

    I am not aware of a technique to do this while maintaining the essential properties that make a log amp attractive for photodiode applications. Op amp circuits added to the input circuitry of a log amp generally inject an error related to the offset voltage of the op amp that creates larger errors in the transfer function at very low input currents.

    In the end, you may do better by making a conventional transimpedance amplifier with an op amp and feedback resistor.

    Regards, Bruce.

  • 0 in reply to Bruce Trump
    Intellectual 370 points

    Bruce,

    Thanks for your reply. We shall try with conventional transimpedance amplifier.

     

    Regards,

    Jayaram C B