I performed the AC analysis of the following circuit:
This is a simple second order LPF satisfying the butterworth filter requirements. According to me after the break point there will be a continuous decrease in magnitude by -40db/decade but this was not the case as seen below:
The pictures shows that the response decreased by almost -40db per decade but it then started to increase uptill a certain point which according to me indicates the presence of a zero. But there is no zero in the T.F of the sallen-key topology. So please can someone explain why this happens?