Abstract
Integration of affinity biosensors with microelectronics has drawn expanding attention since compact, low-cost and real-time systems can be implemented using modern silicon VLSI technology. This thesis presents a CMOS (complementary metal oxide semiconductor) compatible EGFET (extended-gate field effect transistor) sensor with integrated readout circuits to detect the intrinsic charges of DNAs. A new solution for differential readout which can significantly reduce area and power consumption is proposed. A low pass filter in ultra low frequency filtering for biomedical applications is also presented. Based on EGFETs, a label-free platform for monitoring the enzymatic synthesis of single-stranded DNA (ssDNA) in real time is proposed. Protein targets extracted from samples can trigger the DNA amplification using Rolling Circle Amplification in room temperature. With primers immobilized on the surface of EGFETs, periodic ssDNAs were synthesized by RCA. With elongation of DNA, the change of potential at the sensor surface from accumulation of intrinsic charge is recorded as output voltage of the readout circuit. Moreover, the reaction rates dependent on the concentration of proteins are also distinguishable from the responses of the EGFETs. Finally, a circuit technique to reduce ground interference in ultra-low-frequency filtering is proposed.