The temperature coefficient(TC) is a material constant at which certain material properties change as a function of temperature. For example, the resistance and conductivity of metals or the dielectric properties of insulating materials can change.
- For capacitors, the temperature coefficient determines how the capacitance of a capacitor changes with temperature. The linearly increasing temperature coefficient is expressed in millionths of a part per degree Celsius (TC = ppm/°C) or as a percentage with respect to a specified temperature range. There are special ceramic capacitors that have a C0G dielectric (Negatve-Positive-Zero, NP0) specified by the EIA, and their temperature coefficient is much lower than that of classical ceramic capacitors. For most film capacitors, the temperature coefficient is not linear; for these components, the TC value is given as a percentage.
- For most resistors, a change in temperature causes an approximately linear change in resistance value. The temperature coefficient of resistors, the Temperature Coefficient of Resistances( TCR), is denoted by the Greek letter lower case alpha and is expressed in parts per million per degree Celsius (ppm/°C). It can be positive or negative, meaning the resistance value increases or decreases with increasing temperature. However, there are also some alloys that have a temperature coefficient that is approximately zero, meaning that it causes no change in resistance with temperature changes. The positive and negative temperature coefficients are utilized in thermistors, which are used as hot conductors or PTC thermistors in electronic circuitry and for temperature displays.
- In the case of solar modules, which have a strong temperature dependence, the temperature coefficient indicates the percentage by which the output of the solar module decreases with increasing temperature. A small temperature coefficient has the advantage that the efficiency decreases less when the temperature rises.