A 1.2-V 140-nW 10-bit Sigma-Delta Modulator for Electroencephalogram Applications

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.