I'm currently building a filter circuit that is required to remove an DC offset from the raw signal and then amplify the gain. The rest of the circuit (not shown) is a 2-stage LPF with extra gain.
My problem is that when I add a HPF (fc = 0.002Hz) (or any HPF for that matter) at the output after the buffer, I get an offset of -10V. I've tried other op-amp models (LM741, LM324, etc) and the offset occurs but of a much lower value depending on the model. What opamp specification should I look at in the datasheet to determine why this is occurring?
The opamp I'm using is the THS4012.
The input is at 100Hz and is shown as the yellow signal.
The green and red signal are the respective outputs after the buffer.