3 February 2017 High resolution CMOS capacitance-frequency converter for biosensor applications
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Proceedings Volume 10036, Fourth Conference on Sensors, MEMS, and Electro-Optic Systems; 100360F (2017) https://doi.org/10.1117/12.2244148
Event: Fourth Conference on Sensors, MEMS and Electro-Optic Systems, 2016, Skukuza, Kruger National Park, South Africa
This paper presents the design of a low-complexity, linear and sub-pF CMOS capacitance-frequency converter for reading out a capacitive bacterial bio/sensors with the endeavour of creating a universal bio/sensor readout module. Therefore the priority design objectives are a high resolution as well as an extensive dynamic range. The circuit is based on a method which outputs a digital frequency signal directly from a differential capacitance by the accumulation of charges produced by repetitive charge integration and charge preservation1. A prototype has been designed for manufacture in the 0.35 μm, 3.3V ams CMOS technology.

At a 1MHz clock speed, the most pertinent results obtained for the designed converter are: (i) power consumption of 1.37mW; (ii) a resolution of at least 5 fF for sensitive capacitive transduction; and (iii) an input dynamic range of at least 43.5 dB from a measurable capacitance value range of 5 – 750 fF (iv) and a Pearson’s coefficient of linearity of 0.99.
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I. S. Ghoor, I. S. Ghoor, K. Land, K. Land, T-H. Joubert, T-H. Joubert, } "High resolution CMOS capacitance-frequency converter for biosensor applications", Proc. SPIE 10036, Fourth Conference on Sensors, MEMS, and Electro-Optic Systems, 100360F (3 February 2017); doi: 10.1117/12.2244148; https://doi.org/10.1117/12.2244148

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