High-Performance Readout Circuit for Monolithic Integrated Pressure Sensor

Abstract

A readout circuit with high sensitivity and high linearity is proposed in this paper. The applied pressure is sensed by Wheatstone bridge which can reduce the adverse effect of temperature. As the applied pressure changes from 15kPa to 115kPa, the sensitivity of the bridge is 0.36mV/kPa. The current source of the circuit can provide a current with a positive coefficient which can compensate for the inherent high-temperature loss of sensitivity of the Piezoresistive Bridge. Three high-precision operational amplifiers with symmetrical input and rail-to-rail output are used to process the output signal of the bridge. It can provide high CMRR with 123.8dB, open loop gain is 110dB and the output swings from 36.41mV to 4.953mV as the power supply is 5V. A thin film resistors network can compensate for the zero pressure offset and sensitivity by trimming. The high sensitivity of the bridge and the high linearity of the proposed circuit make the readout circuit suitable for monolithically integrated pressure sensor.