What is temperature coefficient of capacitor?

Answer 1

The capacitance value of a capacitor always changes a little as its temperature changes. Small ceramic units will be rated as 5% or 10% tolerance, and a big old electrolytic might have tolerances of -50% to +100% ! Usually, you don't really care what the exact value is, and the variation with temperature doesn't bother you. But there are design situations where you do need to know the exact value of the capacitor ... like maybe you're using it to generate a specific frequency that will then be multiplied a few hundred times in the system's later stages. Or at least you need to know how much the capacitor will change as the circuit gets warm. The temperature coefficient of a capacitor is a number that tells how much the capacitance value will change with temperature. Typically the number tells how many parts per million per degree C, and the number has a sign ... positive or negative. Parts per million: means 0.0001 percent of the nominal capacitance marked on it per degree C: means that much for every Celsius degree of temperature change the sign: tells whether the capacitance value goes up or down when temperature increases. How would you make a capacitor that never changes value, or changes very little with temperature ? ===> Take two capacitors, each with 1/2 the value you need, both with the same temperature coefficient but one positive and the other negative, and install them in parallel. Ideally, as the temperature changes, one capacitor goes up in value and the other one falls, and their sum in parallel is constant.