Signal Conditioning Circuit for CMOS-Based Wheatstone Bridge Stress Sensors

This paper presents the design of an analogue signal conditioning circuit for use with a matrix of CMOS-based Wheatstone bridge mechanical stress sensors. The circuit supplies the bias voltage to the sensors, retrieves the bridge diagonal voltage from the sensors, and amplifies the diagonal voltage with an adjustable-gain instrumentation amplifier. The circuit applies the bias voltage in four orientations across the Wheatstone bridge, enabling the use of the switched voltage method for the stress measurements. The diagonal voltage is retrieved for each bias voltage orientation. The instrumentation amplifier is realised with three operational amplifiers and has an adjustable gain realised by switching between the different gain selection resistors. The amplifier is stable and produces a linear response. The proper operation of the system comprising the three elements is confirmed with the simulations.