Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10409312 | Sensors and Actuators A: Physical | 2011 | 7 Pages |
Abstract
The experimental detection of capacitance variations with a resolution as low as few zeptoFarads (10â21Â 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 1Â 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 by means of a mechanical fixture that converts micrometric linear displacement into sub-aF capacitance steps. The experimental results match the theoretical expectation down to a resolution of 5Â zFrms (6Â V at 100Â kHz, with a 100Â ms time constant). The achieved current resolution of 15Â fArms (at â¼ms time scale) and the tracking of 40Â zF capacitance steps demonstrate how the proposed read-out circuit can serve as a versatile tool for the development of nanosensors.
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Authors
Marco Carminati, Giorgio Ferrari, Filippo Guagliardo, Marco Sampietro,