Improvement of stop-band attenuation for the Sallen-Key low-pass filter

A Sallen-Key low-pass filter configuration with improved stop-band attenuation is presented. The proposed configuration simply connects an additional capacitor which is in parallel to the filter's output to effectively reduce the high-frequency impedance and consequently the undesired high-frequency feedthrough. The relationship between the additional capacitor and high-frequency feedthrough is also investigated to verify its feasibility. The proposed Sallen-Key low-pass filter configuration combines the advantages of simplicity and improved stop-band attenuation which make it attractive for practical application. The simulation and measurement results also confirm the theoretical prediction.