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.