CMOS Analog Correlator Based Glucose Sensor Readout Circuit

Abstract

Recent investigations show research and development of alternative methods of glucose sensing using electrochemical biosensors to help significantly reduce the difficulties associated with treating diabetes. The integration of microelectronic circuit technology with biosensors is generating greater research interest. The advantages of small size and less power consumption of integrated circuits (ICs) are helping with the realization of biosensors for improved performance. The major challenges involving designing of readout ICs for the electrochemical biosensors are accuracy and range. In this research work, an analog correlator based readout circuit for amperometric glucose electrochemical biosensors is designed and implemented. It is designed to work with the output range of a novel microneedle based non-enzymatic painless glucose sensor. This minimally invasive sensor is designed to measure the glucose level of the interstitial fluid in epidermis layer. The analog correlator based readout circuit can achieve the required input current range (5µA to 30µA) from the microneedle based glucose sensor and show a linear output in that range. The analog correlator based glucose sensor readout circuit offers lower noise and wider dynamic range compared to the conventional TIA architecture and is a better solution for the readout circuit for the microneedle based sensor. For the CMOS IC implementation, the analog correlator based readout circuit is designed and fabricated in 0.35um CMOS process. The design and analysis of the individual circuit components including the op-amp and multiplier are presented in this work. The op-amp achieves a 118.3 dB gain and 47.3 degrees phase margin. The circuit DC response for input range of 5uA to 30uA gives a linear output voltage range from 0.21V to 1.38V. The total output RMS noise is simulated to be 6.6mVRMS. The circuit has a mean error of 1.6% and consumes 5.1mW of power. The total area of the proposed readout circuit is 300um × 167um.