A power-saving approach for driving integrated FET gas sensors

A new approach for driving integrated FET gas sensors, performing a current-voltage conversion, and, simultaneously, reducing power dissipation is presented. The proposed approach is experimentally tested on an integrated Porous Silicon JFET (PSJFET) sensor upon exposure to hundreds ppb of NO2. The PSJFET is a p-channel JFET integrating a meso-structured PS layer between drain and source. The PS layer acts as a sensing gate and allows the JFET current to change upon adsorption/desorption of analytes. An electric gate is also available and allows the JFET current to be electrically tuned independently from analytes. A negative feedback loop is used to modulate the electrical gate voltage in order to compensate for PSJFET source-drain current variation induced by adsorption of analytes in the sensing gate, and hence to reduce the sensor power dissipation. The negative feedback loop also allows implementing an intrinsic current-voltage conversion of the sensor signal. Experimental results on the dynamic characterization of PSJFET driven according to the proposed power-saving approach are reported for several NO2 concentrations (up to 500ppb), at room temperature operation.