Design of an integrated low-noise read-out system for DNA capacitive sensors

This paper describes an integrated solution for an accurate DNA label-free detection. The sensor considered is capacitive and constists of two golden electrodes. A known DNA strands (probe) is immobilized over them and a capacitive shift occurs in presence of a complementary sequence inside the solution. The shift amount has been previously evaluated by means of a charge sensitive amplifier (CSA) with an active feedback resistance, followed by a comparator and a counter on a prototyping board. Starting from the measurement results an integrated version is presented here using a low-noise CSA to reduce the low-frequency noise and offset. The system provides an A/D conversion and an evaluation of the capacitive shift amount with a resolution of more than 12 bit. The proposed integrated version of the read-out demonstrates the ability to identify variation on the capacitive values of the sensor with a resolution of 0.1%.