A thermistor is typically made from which material?

• A. Semiconductor material.
• B. Metal.
• C. Plastic.
• D. Ceramic.

Answer: (A)

Thermistors rely on a strong, reversible change in resistance with temperature. That sensitivity comes from the semiconducting nature of the material: as temperature rises, the number of charge carriers in a semiconductor increases and their movement changes, causing resistance to change significantly (decreasing for NTC types or increasing for PTC types). This large temperature coefficient is what makes thermistors useful as precise temperature sensors. Metals change resistance with temperature too, but their coefficient is small, so they don’t provide the needed sensitivity. Plastics are typically insulating and don’t offer the controllable resistive response thermistors require, while ceramics can be active in a temperature-sensitive way when they are semiconducting metal oxides. So the material best fitting a thermistor’s purpose is a semiconductor material.