An active electrode design for weak biosignal measurements

High quality and ambulatory measurements of biosignal, especially some weak biopotential signals with amplitude less than 1 μV is significant for the follow-up applications and is still challenging. This paper presents a new low-noise, high-performance active electrode design for such weak biosignal measurements. The proposed active electrode is designed in the fully-differential configuration in combination with the right-leg driven signal, which is seldom included in the previous design of active electrodes. Main advantages of this design lie in further improving the common-mode interference rejection with introducing right-leg driven signal and ideally driving differential inputs of ADS1299 to extract 1 μν level biosignal from other large noises voltages with the fully-differential configuration. The active electrode achieves 4.52 μVrms (0.5-200 Hz) input referred noise and 96.09 dB CMRR at 10Hz. Two preliminary verification experiments of ECG and EMG were performed using the traditional passive electrodes and the proposed active electrodes for comparison. The results demonstrated the benefits of the active electrode in terms of main interference suppression like power line interference and motion artifacts over the passive electrode. Therefore, the proposed active electrode with low noise and high CMRR could be used in weak biosignal (1 μν level) measurements in the future.