Differential Amplifier Sensor Architecture for Increased Sensor Selectivity

The use of a differential amplifier sensor architecture has been investigated as a route to improved sensor selectivity. Carbon nanotube FETs (CNTFETs) are used as both the transistors in a differential amplifier as well as chemical-sensing elements. Chemical functionalization of the CNTFETs can result in selective sensing. However, functionalized sensors are still likely susceptible to many undesired nonselective sensing events. By functionalizing two FETs differently, one FET can be tailored to selectively sense the analyte, and the other can be used as a reference to compensate for a wide range of interfering signals when the two FET outputs are subtracted. In this way, many interfering events can be discriminated against to yield robust and selective sensing in complex and dynamic environments. Proof of concept experiments showing the utility of background subtraction in software (calculated differential amplifier output) and hardware (using a breadboarded differential amplifier) are shown.