thermoresistive

Thermoresistive describes materials whose electrical resistance changes significantly with temperature. The best-known thermoresistive devices are thermistors, resistors whose resistance decreases with temperature (negative temperature coefficient, NTC) or increases with temperature (positive temperature coefficient, PTC). Thermoresistive behavior arises from changes in carrier concentration and mobility in semiconducting or polymeric materials as they warm or cool.

Common thermoresistive materials include ceramic metal oxide compositions used for NTC thermistors; and doped semiconductors or polymer composites used for PTC thermistors and resettable fuses. NTC thermistors are often used as temperature sensors or for inrush current limiting, because their resistance is high when cold and falls as the circuit warms. PTC thermistors can be used for overcurrent protection and temperature compensation; polymer PTCs are popular as resettable fuses due to their reversible resistance increase when heated.

Performance is described by parameters such as the temperature coefficient (alpha), nominal resistance at a reference temperature, and the nonlinearity of the resistance–temperature curve. Response time, stability, hysteresis, and self-heating affect measurement accuracy. Devices may be calibrated and configured in 2-wire or 4-wire arrangements.

Applications span consumer electronics, automotive sensors, medical devices, and industrial process control. Thermoresistive elements provide simple, reliable temperature measurement and protection, but require compensation or linearization for precise control. Aging, moisture sensitivity (in polymer-based devices), and drift can limit long-term accuracy.