Capacitive Driven-Right-Leg Circuit Design

MARCELO HABERMAN; ENRIQUE SPINELLI; PABLO GARCÍA; FEDERICO GUERRERO

International Journal of Biomedical Engineering and Technology

Inderscience

Año: 2015 vol. 17 p. 115 - 126

1752-6418

Abstract: Capacitive electrodes allow to pick-up biopotentials through a dielectric layer, without using electrolytes and without any charge interchange between electrode and patient body. However, this technique is vulnerable to electric field interference, mainly to common mode voltages produced by the 50Hz power-line. A fully capacitive Driven Right Leg circuit (CDRL) is proposed to reduce the patient common mode voltage vCM. The design of this circuit takes into account several factors as electrode impedance, stray coupling capacitances and amplifier transfer function response. All these parameters are addressed to ensure the circuit?s stability in most biopotential acquisition scenarios. Monte Carlo analyses were performed to find the worst conditions, resulting in a maximum CDRL gain between 70 and 80 dB. This amplification is enough to acquire biomedical signals by means of simple Single Ended (SE) amplifiers. The CDRL was implemented as an independent block that can be used for different applications such as ECG, EMG or EEG. Several experimental results are presented, showing good quality recordings even using SE amplifiers, an appropriate approach for multichannel acquisition systems.