thermistor 2

The volt ampere characteristics of thermistors are also very important, as shown in Figure 6-12. As shown in the figure, at the beginning, there is a good proportional relationship between current and voltage. At this time, the power consumed on the resistor is small, and there will be no self heating phenomenon. The thermistor, as a cold state resistor, is completely determined by the external temperature. As the current increases, the resistor releases heat and heats up itself, causing the resistance value to decrease. The voltage at both ends no longer changes proportionally with the increase of current. Within an interval, the increase in current and the decrease in resistance compensate for each other. At this point, the voltage remains relatively constant until the decrease in resistance exceeds the corresponding increase in current, at which point the voltage begins to decrease. Therefore, the current should be determined based on the allowable power consumption of the thermistor. diode

4. Application of Semiconductor Thermistors Thermistors can be used for temperature measurement, temperature control, temperature compensation, voltage and amplitude stabilization, automatic gain adjustment, gas and liquid analysis, fire alarm, overheating protection, and other aspects.diode

PTC is made by sintering barium titanate (BaTiO3) as the main raw material, doped with elements such as strontium, titanium, zirconium, etc. PTC thermistors are not only used in temperature measurement, control, and protection circuits, but also widely used in household appliances such as color televisions, electric irons, and electronic mosquito repellents.

Figure 6-13 shows the appearance of the domestic M272 series products and the demagnetization circuit of the color TV composed of them. Connect the PTC in series with the demagnetization coil and install it near the explosion-proof zone of the cathode ray tube. After being powered on, a decaying current flows through the demagnetization coil, generating a strong and gradually decaying alternating magnetic field, achieving the purpose of automatic demagnetization.diode