Non linear resistors, Thermistors

Non-linear resistors belong to the family of passive electronic components and, thanks to their unique properties, are used in many areas of electronics. They are characterized by their high sensitivity to temperature, a major drawback for electronic components, but one that is exploited and even reinforced in the case of non-linear resistors.

They are used as series protection elements for electronic circuits, current limiters, temperature detectors and regulators, heating elements, etc.

The special properties of these polycrystalline semiconductors are mainly linked either to the intrinsic characteristics of the crystallites (negative-temperature-coefficient thermistors) or to the characteristics of the grain boundaries (positive-temperature-coefficient thermistors).

This article summarizes the main properties of ceramic thermistors, and shows how recent developments in powder technology and forming methods can be applied to this type of component for use in high-performance electronic applications.

The ever-increasing demand for these components is due to their low cost, ease of assembly and thermal sensitivity. Current technical developments are geared towards miniaturization, and in particular the presentation of these components in the form of "chips" adapted to surface-mount technology on printed circuit boards.