A CMOS Switched Capacitor Based Amperometric Readout Circuit For Microneedle Glucose Sensor

Abstract

Accurate regulation of glucose metabolism is one of the key factors in keeping a healthy state among mammalians. Increase in failure of this natural blood glucose regulatory mechanism has propelled the research for improvements in blood glucose measurement and its regulation. Also, advancement in the research of internet of things has increased the demand for smart sensors creating a revolution in health care industry and which has inturn led to the improvement in point-of-care testing.Therefore in this thesis work a microneedle glucose sensor is chosen as it can be fabricated by MEMS process which allows it to be easily integrated with CMOS integrated circuit in a single package creating a smart glucose sensor. This smart glucose sensor can sense glucose concentration and process the data all in one chip called Lab-on-chip(LOC). To meet architectural requirements of smart glucose sensor such as low power and compact area a switched capacitor based trans-impedance amplifier architecture is chosen as amperometric readout circuit, as the existing circuit architectures consume higher power compared to switch capacitor trans-impedance amplifier architecture.In this work a switched capacitor trans-impedance amplifier is analyzed and designed using an operational amplifier and transmission gates. The integrated circuit layout of the design is prepared for 0.35µm fabrication technology. The total area of the layout is 160µm x 157µm and the area of a 100pF on chip capacitance is 900µm x 50µm. The design is simulated and tested with on chip gain capacitor of 100pF at 200 kHz and with external gain capacitor of 100nF at 200Hz. The circuit linearly amplifies the input current from 2µA-30µA to an output voltage of 45mV-664mV with a trans-impedance gain of 22kΩ. The measured noise at 200 kHz sampling clock is 3mVrms and system power consumed is 1.67mW, whereas measured noise at 200Hz sampling clock is 1.3mVrms and the power consumed is 1.34mW.