A galvanic isolated evaluation of a NTC thermistor using a logarithmic amplifier

This paper presents a possibility to evaluate a NTC (negative temperature coefficient) thermistor, which exhibits an exponential behavior, using a logarithmic circuit. The presented method allows a quicker and precise processing compared to look-up tables or linearizing circuits. The resistance value is converted into a galvanic isolated voltage signal. Furthermore the presented design is optimized for a low current consumption. Both features allow a direct application on the power stage side with a supply given by IGBT driver auxiliary supply.