A 1.2-V 730-nW 10-Hz-3.5-kHz programmable biopotential front-end

Abstract

This paper introduces a power and gain optimized programmable gain-bandwidth ampli¿er as sensor interface of physiological signals for batteryless applications. The proposed interface is divided in two independent stages that use capacitive networks to set the gain and bandwidth. The ¿rst stage is a tunable bandwidth frontend ampli¿er (TB-FEA), which operates from 10 Hz to 3.5 kHz, for processing ECG (electrocardiography), EMG (electromyography) and EEG electroencephalography) signals. The second stage is a programmable gain ampli¿er (PGA), that sets the gain from 37 to 87 dB. The sensor interface adjusts the lower (analog control) and the upper (digital control) cutoff frequencies of the ¿lter. The gain is digitally controlled by a capacitive network in the feedback path of the PGA. The circuit has been implemented in a chip using a 90nm CMOS commercial technology process. The silicon area is 700x700 μm2. The power consumption of the whole sensor interface is 730 nW for a power supply voltage of 1.2 V. Finally, PVT (Process-VoltageTemperature) analysis demonstrates the good performance of the proposed design.