CCII Based Current Signal Interface for Piezoresistive Pressure Sensor

In this paper, we present a current mode interface design for full bridge MEMS piezoresistive pressure sensor utilizing a differential current signal with high sensitivity and linearity. MEMS-piezo resistive pressure sensors are popular as they are small, robust and low cost. Typical sensitivity of these sensors is of the order of few millivolts per Bar. The presented approach utilizes the current signal from the bridge output port and detects ultra-low variations in the sensor thus enhancing the sensitivity. The current mode approach uses two positive second-generation current conveyors (CCII+) in a closed loop fashion thus eliminating the use of negative current conveyor (CCII-). This approach conveys high common mode cancellation, ease of offset balancing, increased sensitivity and eliminates the use of the current source as excitation. The circuit performs trans-impedance conversion through a single ended gain resistance and eliminates the use of any further amplification stages. The performance of the interface design is evaluated in simulation using AD844 of analog devices which represents a functional current conveyor. Moreover, the results are evaluated with a MEMS pressure sensor and are characterized from 0 to 1000mBar using the interface circuit with an achieved sensitivity of 11.7V/Bar.