General Model and Equivalent Circuit for the Chemical Noise Spectrum Associated to Surface Charge Fluctuation in Potentiometric Sensors

This paper firstly reports a general and powerful approach to evaluate the power spectral density (PSD) of surface charge fluctuations, so-called “chemical noise”, from generic set reactions at sensing potentiometric sensors such as, for instance, Ion-Sensitive Field Effect Transistors (ISFETs). Starting master equation, noise signature reaction is derived as function kinetic parameters interface concentration ionic species. Secondly, we derive an equivalent admittance, whose thermal PSD produces equal that fluctuations. We also show how expand this admittance into stair-case RC networks, with number elementary cells involved. can be included in circuit simulations coupled SPICE compact model underlying FET, enable physically based modelling frequency dispersion layer when simulating sensor read-out. Validation existing models literature results well new application examples are provided. The proposed methodology compute rate equations amenable use different contexts where fluctuations generated by random transitions between discrete states given exchange rates.