The thermistor is a component whose resistance value changes with changes in ambient temperature. It is a subcategory of the resistor category. This type of component is classified as [thermistor] in the international component classification.
Thermistors are mainly divided into two categories: PTC (Positive Temperature Coefficient) thermistor and NTC (Negative Temperature Coefficient) thermistor. The resistance value of a PTC thermistor increases as the temperature increases, while the resistance value of an NTC thermistor decreases as the temperature increases.
PTC thermistors can be further subdivided into ceramic PTC (CPTC) and polymer PTC (PPTC). They work on the principle that when the internal temperature exceeds a certain threshold (Curie temperature), the resistance value increases dramatically. This characteristic makes it widely used in overcurrent protection in electrical products. For example, when the current flowing through the PTC is too large, the internal temperature of the PTC rises and the resistance value increases rapidly, thereby limiting the current and preventing circuit damage.
NTC thermistors are mainly made of metal oxides such as manganese, cobalt, and nickel. They exhibit different external characteristics according to different manufacturing processes. For example, the resistance of the MF72 series of NTCs decreases sharply as the temperature increases and is mainly used to weaken the current impact when the device is started; while the MF58 series of NTCs has a linear decrease in resistance as the temperature increases and is mainly used for temperature measurement. .
PTC thermistors are widely used as resettable fuses or resettable fuses because they can automatically return to their original state after overload protection. After the power is disconnected, the heat inside the PTC dissipates and the resistance value returns to the minimum value within about one minute, thus protecting the circuit from damage. These characteristics make PTC thermistors play an important role in the field of overcurrent protection, while NTC thermistors demonstrate their value in temperature control and measurement applications.