one Mistake on top post, with I=0, ie not connecting IDAC, not getting any value on multimeter.
What is Vref (VDAC8) set to ? With a scope is TIA output DC or noisy, 60 cycle, etc.....
Per your diagram Pin_6 = Pin_5 as measure din DC voltage.
The TIA in this circumstance should act as a follower, although you might
want to disconnect the pin from TIA inverting input to minimize pickup for the
To get an offset of .29 V with 40K TIA G set R one would have to have a leakage
of ~ 7 uA, which would be a pretty high bias current for the OpAmp used in TIA.
I looked for Ibias / Ileakage specs on OpAmp, TIA, saw none. This is just an
1 of 1 people found this helpful
I set this up, using 1M Ohm TIA G set R to "aggravate" Ibias and Ileak errors.
For VDAC = 0 I got 29 mV of TIA offset
For VDAC = .512 V I got ~ 3 mV of TIA offset
If you look at G error and zero scale error for DAC that pretty much would cover
the 29 mV I got. To be exact one should calc the spec errors to see what one can