ABSTRACT
This paper presents a second-order Sigma-Delta modulator for electroencephalogram applications with 10 bits of resolution, 1.2 V of supply voltage, and only 140 nW of power consumption over a bandwidth of 25 Hz. Low-voltage operation has been achieved using quasi-floating-gate-based circuits. The use of a new class-AB operational amplifier in weak inversion allows very low power consumption. Experimental results show an energy efficiency of 1.6 pJ per quantization level, making it the most energy-efficient converter reported to date in the very low signal bandwidth range.
ABSTRACT
A low-voltage and low-power front-end for miniaturized, wearable EEG systems is presented. The instrumentation amplifier, which removes the electrode drift and conditions the signal for a 10-bit A/D converter, combines a chopping strategy with quasi-FGMOS (QFG) transistors to minimize low frequency noise whilst enabling operation at 1 V supply. QFG devices are also key to the A/D converter operating at 1.2 V with 70dB of SNR and an oversampling ratio of 64. The whole system consumes less than 2uW at 1.2V.