Now that it has been decided what to build, it must be decided how to build it. That means it is necessary to decide which of the filter topologies to use. Filter design is a two-step process where it is determined what is to be built (the filter transfer function) and then how to build it (the topology used for the circuit).
In general, filters are built from one-pole sections for real poles, and two-pole sections for pole pairs. While a filter can be built from three-pole, or higher order sections, the interaction between the sections increases, and therefore, component sensitivities go up.
It is better to use buffers to isolate the various sections. In addition, it is assumed that all filter sections are driven ...