A Voltage Domain Code Division Multiplex Based Analog Front End For Energy-Efficient Multi-channel Bio-potential Acquisition

This paper proposes a voltage domain code division multiplex based analog front end for multi-channel bio-potential acquisition. Implemented with switched-capacitor multiplying digital-to-analog converters, multiple biopotential signals are modulated simultaneously into a single channel and amplified, which reduces hardware cost and power consumption. Furthermore, chopper is used to reduce the low frequency noise from the amplifier. The proposed circuit structure is verified in an 8-channel acquisition system with 180 nm CMOS process. The simulation results demonstrate an inter-channel crosstalk of -64 dB with an overall voltage gain of 26 dB, input referred noise of $1.54 \mu \mathrm{~V}$, while the entire system dissipates $8 \mu \mathrm{~W}$/channel.