A low-voltage boostrapping technique for capacitive MEMS sensors interface

A low-voltage, low-noise pre-amplifier for MEMS capacitive sensors is here reported. The presented circuit uses boostrapping technique applied on both terminals of the sensor, thus exploiting the sensor parasitic capacitances in order to increase the signal voltage level, without affecting the Signal-to-Noise Ratio. In the proposed circuit, both terminals of the sensor are floating and biased through large resistors. The boostrapping technique adopts a two nested-path positive feedback, acting through the substrate parasitics. Experimental results agree with simulations, exhibiting a total signal level boosting of 20 dB.