Sensori e Interfacce per l'Industria e la Biomedica

The design and development of sensor readout circuits are fundamental to modern signal processing systems. This research study focuses on investigating, designing, and analyzing novel circuits for sensor interfacing, especially for industrial and biomedical fields. A broad range of original oscillator-based and bridge-based conditioning circuits are discussed and analyzed. A significant contribution is the exploration of second-generation voltage conveyor oscillators, for which 34 novel VCII-based sinusoidal oscillator circuits have been discovered. Among these, 30 schemes are single-frequency oscillators, while the remaining 4 can also be used as variable-frequency oscillators. These circuits are particularly suitable for resistive and capacitive sensor interfacing. For the case in which these VCII interfaces have to be implemented on an integrated circuit, the design of a new low-voltage, low-power VCII topology in 150 nm CMOS technology is also presented. This design aims to represent a valid alternative to commercial VCII when low-power battery-powered portable applications are of concern, as is often the case. Concerning bridge-based interfaces, this research study also presents a novel bridge interface specifically designed for a research-level biomedical sensor used for NaCl concentration measurement. Differently from other solutions reported in the literature, the proposed interface has the advantage that it can also be used with non-purely resistive or capacitive sensors, such as the one considered here. Experimental and simulation results are reported for all the proposed solutions. These validate the theoretical treatment of the analysis performed and provide insight about the circuit performance. The obtained results confirm the suitability of the proposed schemes for implementing sensor interfaces meant to be used with several industrial and biomedical sensors in a broad range of applications.