Silicon carbide based instrumentation amplifiers for extreme applications

While instrumentation amplifiers based on silicon technology have revolutionized our understanding of the world in which we live, they are limited to operating in benign environments. This limitation precludes their use in a wide range of industrial, automotive and geological applications, where the required operating temperatures can exceed 200° C. Silicon-on-insulator technology has enabled the development of high temperature electronics, however applications requiring higher temperature operation are becoming apparent. In this work, we present the integration of JFET structures to demonstrate high gain amplifier circuits capable of operating at temperatures up to 400C. The circuit design is supported by the realisation of a novel JFET compact model, which enables a greater level of confidence than existing models in the literature. The experimental open loop gain of a two stage differential amplifier is 45dB at room temperature and this equates to a sensitivity of 55mV/°C for a Pt100 thermometer, which is sufficient for the monitoring of a range of industrial processes.