Design Low-Pass, High-Pass, and Band-Pass Filters in Browser in Minutes | via @adi_news « Adafruit Industries – Makers, hackers, artists, designers and engineers!
Sallen-Key Low-pass Filter Design Tool
Sallen-Key Low-pass Filter Design Tool
Low Pass Filtering Calculator, Simulation, and Theory :: The Quantizer
Low Pass Filter Calculator - ElectronicBase
Active Low Pass Filter Circuit Design and Applications