SPICE macromodel of silicon-on-insulator-field-effect-transistor-based biological sensors

A user-friendly behavioral macromodel for biological response of FET-based transistors has been developed for use with commercial SPICE versions and will enable circuit level analysis of biosensor chips. The model is based on the physically realistic representation of biological layers using an ion-permeable charged membrane model. Simulations demonstrate good agreement to experimental results. Logarithmic increments in bound membrane charge result in linear threshold voltage shifts. The model accounts for phenomena such as Debye screening of biomolecules resulting in reduced sensor response to increments in salt concentration. Additionally, the presence of site binding charge on oxide surfaces is shown to severely deteriorate sensitivity.