Low power current-mode analog front-end for biomedical applications

Biopotential signals such as Electrocardiogram (ECG), Electromyogram (EMG), Electroencephalogram (EEG), etc. have very small amplitudes and low frequencies. One of the most important component in a biomedical electronic detection system is the biopotential acquisition device. In this paper, a new current-mode analog front-end for biopotential signal acquisition is proposed. It consists of a programmable gain current-mode amplifier (PGC-MA) and a second order current mode low-pass filter (C-MLPF). The implementation of the amplifier and the low-pass filter was done using Externally Linear Internally Nonlinear (ELIN) circuits. The ELIN blocks were implemented using log-domain circuits. Due to this approach, the gain (G) of the PGC-MA, corner frequency (ω0), quality factor (Q) and gain (A) of the C-MLPF, can be tuned using some bias currents. To decrease the power consumption, CMOS transistors operating in subthreshold region were used. The basic building blocks were implemented on a 180nm CMOS process. Spice simulations were performed to validate the proposed solution.