A thermistor, or thermally sensitive resistor, is a resistor which changes resistance in response to a change in temperature. There are two basic types of thermistors, NTC or Negative Temperature Coefficient and PTC or Positive Temperature Coefficient thermistors. NTC thermistors exhibit a decrease in resistance when temperature rises. PTC thermistors exhibit an increase in resistance when temperature rises. QTI manufacturers both PTC and NTC thermistors in a broad selection of package styles and resistance values.