Positive Temperature Coefficient (PTC) thermistors are temperature-sensitive resistors that exhibit an increase in resistance with rising temperature. They are composed of ceramic materials, usually based on barium titanate, which undergoes a phase transition at a specific temperature.
At lower temperatures, PTC thermistors have a relatively low resistance due to the crystalline structure of the ceramic material. In this state, the material allows a significant flow of electric current. As the temperature increases, the ceramic material undergoes a phase transformation, causing its crystalline structure to change.
During this phase transition, the resistance of the PTC thermistor sharply increases. The increase in resistance is a result of reduced electron mobility within the transformed crystalline structure. This change in resistance is particularly abrupt over a small temperature range, making PTC thermistors highly sensitive to temperature variations.
One of the primary applications of PTC thermistors is as a self-regulating heating element. When used in a circuit, the PTC thermistor can limit the current flow and regulate the temperature. As the temperature rises, the resistance of the PTC thermistor increases, leading to a reduction in current flow and, consequently, limiting the amount of heat generated. This self-regulating property makes PTC thermistors useful for applications like overcurrent protection and temperature control in various electronic devices.
In summary, PTC thermistors function based on the temperature-dependent change in resistance of ceramic materials. This property is harnessed in electronic circuits to provide self-regulating temperature control and overcurrent protection.
