Capacitance to voltage converter design for biosensor applications
Taşdemir, Ferhat (2011) Capacitance to voltage converter design for biosensor applications. [Thesis]
Official URL: http://192.168.1.20/record=b1378239 (Table of Contents)
Due to advances in MEMS fabrication, Lab-on-Chip (LoC) technology gained great progress. LoC refers to small chips that might do similar works to equipped laboratory. Miniaturization of laboratory platform results in low area, low sampleconsumption and less measurement time. Hence, LoC with IC integration finds numerous implementations in biomedical applications. Electrochemical biosensors are preferred for LoC applications because electrochemical biosensors can be easily integrated into IC designs due to electrode-based transducing. Capacitive biosensors are distinctive in electrochemical biosensors because of their reliability and sensitivity advantages. Therefore Interdigitated electrode (IDE) capacitor based biosensor system is preferred for development of biosensor platform. In this thesis, capacitive biosensor system with new Capacitance to Voltage Converter (CVC) designs for LoC applications is presented. Multiple IDE capacitor sensing and varactor-based compensation are new ideas that are presented in this thesis. Proposed system consists of five blocks; IDE Capacitor based tranducer, CVC, Low-Pass Filter, Linear LC-Tank Voltage Controlled Oscillator (VCO) and Class-E Power Amplifier (PA). System building blocks are designed and fabricated using IHP's 0.25 µm SiGe BiCMOS process because of its advantage at high frequency and post-process that IHP offers. Varactor tunable CVC design provides highly linear relationship between output voltage and capacitance change in sensing capacitor. Varactor is used in reference capacitor to compensate changes in sensing capacitor. Total chip area is 0.4 mm2 including pads. 10 MHz operating frequency is achieved. Total power consumption changes between 441 µW and 1,037 mW depending on the sensor capacitance.
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