Silicon Carbide Differential Amplifiers for High-Temperature Sensing

摘要

This paper presents silicon carbide sensor interface circuits and techniques for MEMS-based sensors operating in harsh environments. More specifically, differential amplifiers were constructed using integrated, depletion-mode, n-channel, 6H-SiC JFETs and off-chip passive components. A three-stage voltage amplifier has a differential voltage gain of ～50 dB and a gain-bandwidth of ～200 kHz at 450°C, as limited by test parasitics. Such an amplifier could be used to amplify the signals produced by a piezoresistive Wheatstone bridge sensor, for example. Design considerations for 6H-SiC JFET transimpedance amplifiers appropriate for capacitance sensing and for frequency readout from a micromechanical resonator are also presented.