Single-supply, 2nd-order, multiple feedback low-pass filter circuit

[@MysticMonster7]

concise & thorough presentation. thank you!

[@buitenb]

Thanks for this nice but easy circuit !

[@c4alexc4]

Why did you use a 1.25V reference voltage? The output is offset by 2.5V, so why is the offset double the reference voltage?

[@thomasjoseph9948]

gain for NI signal is 2

[@qingli619]

Doesn't it say the gain is -1 ?