  This paper deals with the design of MEMS using piezoresistivity as
transduction principle. It is demonstrated that when the sensor topology
doesn't allow a perfect matching of strain gauges, the resolution is limited by
the ability of the conditioning circuit (typically a Wheatstone bridge) to
reject power supply noise. As this ability is strongly reduced when an offset
voltage is present at the output of the bridge, the proposed architecture
implements a feedback loop to control MOS transistors inserted in the
Wheatstone bridge to compensate resistor mismatches. This feedback exhibits a
very good offset cancellation and therefore a better resolution is achieved.
