A low-power, high-resolution, adaptive sensitivity readout circuit with selective detection range for capacitive biosensors

In this paper, the design and implementation of a low-power, high-resolution, fully differential readout architecture for capacitive sensing applications is presented. The proposed sensing mechanism is based on the gain variations of two capacitively coupled operational transconductance amplifiers (OTAs). The target analyte acts as the dielectric of a sensing electrode, and its detection results in capacitance variations. These capacitance variations are translated to voltage, and the result is amplified to be used as a biomarker detector. With high-gain OTAs and a high-gain difference amplifier, the proposed mechanism achieves a high-resolution of 1 aF, with a sensitivity of 290 mV/fF. The proposed structure exhibits such a high-resolution while maintains an extremely low-power consumption of 6.6 mu W. Using perfectly matched elements with accurate layout, this structure is able to reduce the mismatch-based errors to less than 0.05%. An 8-bit control word adjusts the sensitivity and the detection range of the proposed structure which results in a wide dynamic range of 100 dB. The main features of the proposed structure such as high-resolution, high-sensitivity, low-power consumption, selective capacitance detection range and adaptive sensitivity, make this readout mechanism an ideal solution for sensitive, low-power, and accurate life science biosensors.