Design of a Precision Twin-T Notch Filter for 50Hz Noise Suppression

Design, analysis, and simulation of a Twin-T notch filter using operational amplifiers (Op-Amps), specifically targeting the attenuation of 50 Hz power line interference. The filter architecture integrates a third-order Butterworth low-pass filter (LPF) and a third-order high-pass filter (HPF), combined through a summing amplifier to form a precise and stable notch filter. LPF and HPF sections are designed with a cutoff frequency of 50 Hz, ensuring a maximally flat response in the passbands with sharp roll-offs around the notch frequency. Simulation results from LTSpice validate the theoretical design, demonstrating effective suppression of unwanted frequencies with minimal signal distortion. Twin-T configuration, enhanced with active Op-Amp buffering, achieves deeper rejection and better frequency selectivity compared to existing notch filter designs. The final circuit exhibits a notch at approximately 49.7 Hz with controlled phase response and minimal attenuation of adjacent frequencies, making it suitable for applications in audio processing, communication systems, and biomedical instrumentation. A comparative analysis confirms superior performance in notch sharpness, bandwidth control, and stability. Future improvements may include implementing variable components for tunability across a wider frequency range, further expanding its application scope in adaptive signal processing environments.