Hello everybody,

I designed 8th order low pass filter based on sallen key topology. Tested its transfer function in multi sim and it looked great, but when I assembled it turned out that filter shift DC level of bipolar +-10V signal and halved it. So when I feed in +-10V signal I get -100mv..-10,1V signal. Despite shifted DC level, filter has a correct transfer function, so I am a little lost. What have done wrong?

Thanks in advance.