Transimpedance amplifier calculating feedback capacitor
Both are correct.  

The 1st is an example with equality (=) that includes   Ci, (the junction capacitance of the photodiode in parallel with the input capacitance of the op-amp).  

This is wise, with conservative 60% GBW for choosing \$f_p\$

The 2nd shows Cf "&lt;&lt; an upper limit" for reference  (&lt;&lt; bigger limit than above.)

You need to update your question with datasheets, schematic and measurements.

This is how Honeywell does it.


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