Why would we use MFB filters over a regular filter?

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Fredje

Joined Jun 1, 2022
15
I am learning about multiple feedback filters but had a question that i can't find online or in the textbook. I understand that MFB filters are filters with multiple feedback loops, but I was asking myself what the advantage is of this implementation over a regular one.

For example why would we chose to use a MFB second order lowpass filter over a normal second order lowpass filter?
 

Ian0

Joined Aug 7, 2020
5,489
MFB filters can have gain of less than unity and have an inverting output, which are two things that S&K filters can't do.
 

RPLaJeunesse

Joined Jul 29, 2018
214
Depending on the op-amp design the input offset voltage can change significantly with common mode voltage, particularly with parts having a "rail-to-rail" input range. Using such parts in Sallen-Key filters can add distortion to your signal, usually an undesired effect. The MFB approach keeps the common mode voltage fixed at a design-determined point, significantly reducing the possiblity of common mode induced distortion.
 
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