Design of 50 Hz notch filter circuits for better detection of online ECG

Technological evolution in bio-signal processing has enabled computer-based analysis of ECG which is an adjunct to the doctor in terms of feature extraction and diagnosis. However, acquisition and reliable parameter extraction of ECG signals using a computer based system is extremely susceptible to power line interference. 50 Hz active analogue notch filter is used to trim down hum in such applications. An attempt has been made to design various 50 Hz active notch-filter topologies in P-spice. Based on their amplitude and phase response, add-on notch filter hardware is developed and used with real-time computer based ECG system. The amplifier system includes biosensors, cascaded amplifiers, right leg drive circuits, active filters and 50 Hz notch filters. Analogue output of amplifier system is interfaced to the computer for recording and analysis. Thus a computer based compact and enhanced signal acquisition system is developed that yields online ECG of greatest clinical use.