OPA861 for I/V

[canvas]

Your .1uf coupling cap into 100kohm is giving a -3db at 15hz, this is the tilt your seeing at 1k. You need to either increase the coupling cap to say .33uf or more.

Cheers George

Yes. I used the calculator here. It gives me exactly the value you stated. However, I don't have good qualified capacitor, so I give up. For now, using a pot for DC trimming seems better. I observed No LF problem, but my 20k pot (Vishay 20 turns) is not easy to fine tune the DC center. Will change to 2 fixed 10k + 1k pot.

Poting

 

[SandroN]

Canvas, you say your DAC stack gives 3.5mA output. It is too much for 1.8k I-V resistor.
V=RI => V= 6.3V. Use max 3.6V for OPA861

 

[canvas]

Canvas, you say your DAC stack gives 3.5mA output. It is too much for 1.8k I-V resistor.
V=RI => V= 6.3V. Use max 3.6V for OPA861

Hi,

If you read the datasheet carefully, it's ±3.6 which equals to 7.2Vpp. In fact, I use 2k vishay now. 2000*0.0035=7Vpp. In real world, 0dBFS gives me 6.92Vpp on oscilloscope.