Termistor

A thermistor is a type of resistor whose resistance varies significantly with temperature. This property makes thermistors useful in various applications, including temperature measurement, temperature compensation, and self-resetting overcurrent protection. Thermistors are classified into two main types: negative temperature coefficient (NTC) thermistors and positive temperature coefficient (PTC) thermistors.

NTC thermistors have a resistance that decreases as temperature increases. This behavior is due to the increased thermal energy causing more charge carriers to be available for conduction. NTC thermistors are commonly used in temperature sensors, self-regulating heating elements, and inrush current limiters.

PTC thermistors, on the other hand, have a resistance that increases with temperature. This is because the increased thermal energy causes more defects in the crystal lattice, which act as scattering centers for charge carriers. PTC thermistors are used in self-resetting overcurrent protection devices, such as resettable fuses, and in temperature-compensated circuits.

Thermistors are typically made from semiconducting oxides, such as manganese, nickel, cobalt, iron, or copper oxides. They are available in various shapes and sizes, including beads, discs, and rods, and can be used in both analog and digital circuits. The resistance of a thermistor is typically specified at a reference temperature, usually 25 degrees Celsius, and can vary significantly with temperature.