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OPA855: OPA855 TIA for Homodyne Balanced Detector

Julien Mellaerts
Prodigy 10 points
Part Number: OPA855

Tool/software:

Hello,

I'm trying to design a Homodyne Balanced Detector using OPA855. I'm using two photodiode with bandwidth 145MHz and 12pF capacitance generating 900uA/1mA photocurrent each. I'd like to read the current generated by the HBD (the difference between both photocurrent) at 100MHz rate, thus the TIA should be compliant with this bandwidth. 

I started to design something but I need your help to select right Rf and Cf values for my application, can you please give me insights for these values and also if the design looks correct ? 

Here is my actual design:

Also should I add a load resistor at Vout ? 

Thank you.

  • 0
    TI__Mastermind 28475 points

    Hello Julien,

      Thank you for reaching out. Is each diode 12pF or 12pF total input capacitance to the input of the amplifier?

       For initial testing, we usually recommend using a load resistance similar to what is specified in the datasheet. What is your end application, will you need to interface with an ADC?

    Thank you,

    Sima