termistores

A thermistor is a type of resistor whose resistance is strongly dependent on temperature, more so than in standard resistors. The word "thermistor" is a portmanteau of "thermal" and "resistor". Thermistors are widely used as temperature sensors. The two types of thermistors are NTC (Negative Temperature Coefficient) and PTC (Positive Temperature Coefficient).

In an NTC thermistor, the resistance decreases as temperature increases. This is due to the presence of semiconductor material. As the temperature rises, more charge carriers are freed, increasing conductivity and thus decreasing resistance. NTC thermistors are commonly used in temperature measurement and control applications.

In a PTC thermistor, the resistance increases as temperature increases. These are often made from ceramic materials. Above a certain "Curie temperature," the resistance of a PTC thermistor rises sharply. This makes them useful for overcurrent protection and self-regulating heating applications.

The primary advantage of thermistors is their high sensitivity to temperature changes, allowing for precise measurements. However, they are not as accurate over very wide temperature ranges as some other temperature sensors, and their non-linear behavior requires careful calibration or linearization in circuitry. They are relatively inexpensive and robust, making them suitable for many consumer and industrial applications.