Ultra-high input impedance buffer for dry or capacitive electrodes: Design and characterization for industry

A large number of health and wellness applications wish to monitor electrocardiogram signal (ECG) in the least intrusive way possible. The use dry textile electrodes with high input impedance bio-amplifiers is a common technique. This paper presents novel ultra-high buffer obtain reduced capacitance enhance acquisition results for or non-contact capacitive ECG electrodes. Based on different bootstrapping techniques, stage biasing unipolar power supply, an operational amplifier implemented Printed Circuit Board (PCB) provide low cost solution. solution considers protections electrostatic discharges (ESD) filters interferences, maintaining design. method measure impedances range femtofarads also proposed. active electrode prototype 191 fF at 50 Hz. Different skin-electrode cases are studied Common Mode Rejection Ratio (CMRR). As result, value 81.4 dB obtained zero mismatch 76.1 Hz resistive 1-2.2 MΩ. Moreover, test evaluated using discrete back-end circuit, digital filtering software display. Finally, full circuit has been simulated under ESD transient ±8 kV IEC 61000-4-2 waveform. demonstrated that proposed standard components fulfills industry requirements robust sensor.