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OPA857: Balanced photodiode configuration

Joselito Go
Expert 4590 points
Part Number: OPA857
Other Parts Discussed in Thread: OPA855, OPA856

Tool/software:

Hi Experts,

I'd like to know what would happen if the OPA857 is connected to a balanced photodiode configuration. This means that the OPA857 will have sink and source current from the balanced photodiodes. I need to amplify the current before interface it to and ADC.

Regards,

Josel

  • 0
    TI__Genius 11485 points

    Hi Josel,

    This device should have no issue sinking current from the balanced photodiode. The issue becomes sourcing current to the photodiode. This is because the device is configured to have a fixed output reference voltage of 5/9th of the supply voltage. This means there is not much headroom for the output to swing higher, which is required when sourcing current. The device was designed to sink current from a photodiode. We do have devices such as the OPA855 and OPA856, which can be used as TIAs and are much more versatile than the integrated OPA857.

    Best Regards,

    Ignacio