An apparatus includes a thermistor having a variable resistance with a first dependence on absolute temperature. The apparatus includes a reference resistor having a resistance with a second dependence on absolute temperature, the second dependence being less than or having opposite polarity to the first dependence. The reference resistor includes a switched-capacitor circuit. The apparatus includes a node coupled between the thermistor and the reference resistor. The node is configured to provide a signal indicative of absolute temperature based on the variable resistance and the reference resistance. The signal may be strain-invariant, proportional to a reference voltage, and indicative of a ratio of the variable resistance to the reference resistance. The apparatus may include a feedback circuit configured to maintain the node at a predetermined voltage level.