A sub-μW 36nV/√Hz chopper amplifier for sensors using a noise-efficient inverter-based 0.2V-supply input stage

In low-bandwidth, low-noise applications of wireless sensor nodes, the sensor front-end amplifier presents a power-consumption bottleneck since its current draw is noise-limited and cannot be scaled with the low data-rate, as is possible with the DSP and RF blocks. EEG monitoring is one application where designers have targeted sub-microvolt input-referred noise over a signal band of 0.5 to 100Hz [1]. Prior work to improve the energy-efficiency of low-noise instrumentation amplifiers (LNIAs) for sensors includes chopper IAs [1,2], inverter-based LNAs [3], current-reuse through amplifier stacking [4], and low-supply-voltage amplifier design reaching 0.45V [5].