The rotary angle sensor potentiometer’s output passes through an R-C low-pass filter (not mandatory but proposed) and into the MCP6002 op-amp. The MCP6002 op-amp is configured as a unity-gain buffer, ...

Circuit analysis, a detailed BoM, ... On the input, a MCP6002 rail-to-rail op-amp amplifies and filters the analog waveform and then a MCP3202 ADC digitizes it to a 12-bit signal.

He then plugs the notch filter into the feedback loop of an MCP6002 op-amp, ... This circuit simply amazed me. I never would have thought such a good oscillator could be made with only R and C.