An instrument-on-chip for impedance measurements on nanobiosensors with attoFarad resoution

This paper deals with the design, realization and test of a very-high-resolution and totally integrated impedance-characterization system-on-chip fabricated in standard CMOS technology. The chip architecture is based on a lock-in technique, using the scheme reported in the given figure. It comprises a high-sensitivity input current-to-voltage converter, an analog multiplier and a high-resolution (20b) DeltaSigma analog-to-digital converter. All these stages contain unique features devoted to noise reduction, and their successful integration allows for a very high resolution, down to the attoFarad range, within a 1s time scale.