ZeptoFarad resolution CMOS read-out circuit for nanosensors

Abstract The experimental detection of capacitance variations with a resolution as low as few zeptoFarads (10 −21 F) is presented. This is achieved by means of a CMOS ultra-low-noise and wide-bandwidth current sensing circuit coupled to a lock-in amplifier to perform capacitance and conductance measurements in a frequency range from DC to 1 MHz. The adoption of an integrated implementation, based on an original circuital topology, provides miniaturization and performance improvement. The mm-sized chip can be easily integrated in extremely compact sensing setups. Resolution limits are analyzed in detail and experimentally investigated. The achieved current resolution of 15 fA (at ∼ms time scale) and tracking of 40zF capacitance steps demonstrate how the proposed readout circuit can serve as a versatile tool for nanosensor development.