LMP2234: Why is 16.93mV at the input of LM2234 in TIA circuit ？

Amplifier has input bias current, LMP2234 is one ultra-low input bias current precision amplifier , and its input bias current has only +-20fA (typical value) and the max +-1pA,+-50pA. So the Iib*R3 would generate the voltage on VF2.  

If you used the tiny current measurement with TIA, you could remove the R3 .

Dear Kailyn,

     Thanks  for  your  reply.

    The R3 is  parasitic resistance of photodiodes  and  it can not be  removed. 

     It is  strange that i  used LMV721 to replace lmp2234, the  voltage is only 29.86uV, but its input bias current is 260nA (typical).  Its current is bigger than ones of  lmp2234,but the voltage is smalller than ones of lmp2234.

Best Regards

Devin

I would set up the same circuit as above to simulate again. And I will reply you as soon as possible.

Thanks ！