I would like to integrate a sinusoidal voltage with an amplitude of 630mV at 160Hz. After integrating I schould get a cosine curve. I simulated the integrator circuit in LtSpice. For the first 50ms everything looks good (see attachment) but for longer simulation times the output voltage of the integrator rises until it has swung into a mean value. The progression of the curve looks like an exponential function. I can't find anything about this phenomenon. Is there somebody, who can explain this? Or is it a problem of visualization of LTSpice? What values of the timeconstant τ1=R1*C1 and τ2=R2*C1 do I need.

Thank you for your support