I am trying to make a circuit that will take an RTD and a thermistor (not at the same time). I was thinking simple and using a simple divider into an op amp. Switching out out resistor values is not a problem. For the thermistor, I would use an op amp as a buffer, but when I switch to an rtd, i would change it to a non inverting op amp. It sounded feasible until i saw how everyone uses an active current source for an RTD usually. So...I thought to use a current source for both, but small current through the huge resistance of a thermistor does not sound right.... Anyone every try such a thing?