Introduction
Physics Today paper
The basics
Figure 4
Schematic bias circuits for two kinds of resistive thermometer. A semiconductor thermistor (left) shows a decrease in resistance with increasing temperature, whereas a superconducting transition-edge sensor (right) increases in resistance with increasing temperature within its superconducting transition. The choice of constant current bias for the former and constant voltage bias for the latter results in both devices exhibiting negative electrothermal feedback --- that is, the Joule power (I2r = V2/R) decreases as the temperature is raised.
