Sallen-Key topology
The standard way to build a second-order active filter around one op-amp, two resistors, and two capacitors. Higher-order filters are cascades of these biquad sections — an 8th-order filter is four Sallen-Keys in a row.
In practice
The unity-gain version realizes the stage's Q through a component ratio (C1/C2 = 4Q² for low-pass), which is why sharp filters demand awkward part spreads. Build lowest-Q stage first in the cascade to keep internal nodes from clipping.