Difference between PTC thermistor and NTC thermistor

时间:2019-05-21 丨 预览:102 人次

Both PTC thermistor and NTC thermistor are thermistors. According to different temperature coefficients, it is divided into positive temperature coefficient thermistor (PTC) and negative temperature coefficient thermistor (NTC). The positive temperature coefficient thermistor (PTC) has a larger resistance value at a higher temperature, and the negative temperature coefficient thermistor (NTC) has a lower resistance value at a higher temperature. They both belong to semiconductor devices.

PTC thermistor refers to a thermistor phenomenon or material that has a sharp increase in resistance at a certain temperature and a positive temperature coefficient. It can be used specifically as a constant temperature sensor. This material is a sintered body with BaTiO3 or SrTiO3 or PbTiO3 as the main component. A small amount of oxides such as Nb, Ta, Bi, Sb, Y, and La are doped to conduct semi-conductivity by controlling the atomic valence. Semiconducting BaTiO3 and other materials are referred to as semiconducting (bulk) porcelain; at the same time, oxides of Mn, Fe, Cu, Cr and other additives that increase its positive resistance temperature coefficient are added. High-temperature sintering makes semiconducting platinum titanate and its solid solution, so as to obtain thermistor materials with positive characteristics. The temperature coefficient and Curie point temperature vary with the composition and sintering conditions (especially the cooling temperature).

NTC thermistor refers to the thermistor phenomenon and material with negative temperature coefficient which decreases exponentially with increasing temperature. This material is a semi-conductor ceramics made by fully mixing, forming, and sintering two or more metal oxides of manganese, copper, silicon, cobalt, iron, nickel, zinc, etc., and can be made with negative temperature coefficient (NTC) thermistor. Its resistivity and material constant vary with the proportion of material composition, sintering atmosphere, sintering temperature and structural state. Now there are non-oxide NTC thermistor materials represented by silicon carbide, tin selenide, tantalum nitride, etc.

NTC thermal semiconductors are mostly oxide ceramics with spinel structure or other structures, which have a negative temperature coefficient, and the resistance value can be approximated as:

Rt = RT * EXP (Bn * (1 / T-1 / T0)

In the formula, RT and RT0 are the resistance values at temperatures T and T0, respectively, and Bn is the material constant. The ceramic grain itself changes the resistivity due to temperature changes, which is determined by the characteristics of the semiconductor.

PTC thermistor is a kind of thermistor. The resistance value of the positive temperature coefficient thermistor shows a stepwise increase with the temperature of the PTC thermistor. The higher the temperature, the greater the resistance value.