Tempco

Tempco, short for temperature coefficient, is a parameter that describes how a physical quantity changes with temperature. In electronics and materials science it is usually expressed as a fractional change per degree Celsius, commonly in parts per million per degree Celsius (ppm/°C). For resistance, the temperature coefficient of resistance (TCR) is defined as TCR = (1/R0) dR/dT. Similarly, the temperature coefficient of capacitance (TCC) and of inductance (TCL) describe how those properties vary with temperature. Positive tempco means the property increases with temperature, while negative tempco means it decreases.

Materials and devices with low or near-zero tempco are valued for stability. Examples include certain metal films and dielectrics engineered for minimal drift. Thermally sensitive components, such as thermistors, have large tempco values and are used for temperature sensing or for compensation in circuits; NTC (negative tempco) devices decrease in resistance as temperature rises, while PTC (positive tempco) devices increase. In capacitors, dielectric materials exhibit various TCCs, which is a major factor in capacitor stability over temperature.

Measurement and design considerations: manufacturers specify acceptable tempco over a given temperature range, and designers account for drift by selecting components with appropriate tempco or by implementing thermal compensation in the circuit. Tempco can be nonlinear, so the temperature dependence is often provided as a curve rather than a single number. Manufacturing variations also contribute to tolerance in tempco values, making careful specification important in precision applications.

See also: coefficient of thermal expansion, drift, temperature stability.