I want to create an sine wave from a uC PWM with a very low DC offset. I did some research and decided to simply make a Band-Pass filter, composed by one pole passive High Pass Filter, to filter the DC component, followed by an active 3-pole sallen key filter to make the square wave sine-ish. The result is the circuit in the figure bellow.
At the breadboard i didn't face any significant problems, i got a wave with a good sine shape and with a low dc offset(10mV), but now on the PCB i'm having a significant DC offset (100mV) at the output. I tracked the signal with oscilloscope and this DC shows up right after the HP filter, in the node between R25 and R26.
Does anyone has a hint on what is going on and how can I reduce it?
Edit: PCB layout added. I applied the cooper plan in top and bottom with ground signal. I placed several vias to avoid the ground loop.