Subthreshold transistor operation for a high sensitivity capacitive sensor

In this paper a low-power highly sensitive capacitor sensor is presented. When interfaced to interdigitated electrodes the corresponding circuit, based on capacitance variation, allows sensing microfluidic substances in lab-on-chip applications. We demonstrate the impact of the subthreshold region of transistor on the sensitivity of the capacitive sensor while it decreases the power consumption of the circuit. The proposed capacitive sensor circuit is implemented in 0.18 mum CMOS technology and the obtained sensitivity is 69 mV/fF.