The capacitance of an RC circuit can be affected by temperature changes. The extent of this effect depends on the type of capacitor used in the circuit. Different capacitor materials exhibit different temperature coefficients of capacitance. The temperature coefficient of capacitance (TCC) is a measure of how much the capacitance changes with temperature.
Positive Temperature Coefficient (PTC): Some capacitors, like ceramic capacitors, have a positive temperature coefficient of capacitance. This means that as the temperature increases, their capacitance also increases. Conversely, when the temperature decreases, their capacitance decreases. The effect is generally small but can be significant in certain applications.
Negative Temperature Coefficient (NTC): Other capacitors, such as tantalum and aluminum electrolytic capacitors, have a negative temperature coefficient of capacitance. This means that as the temperature increases, their capacitance decreases. Conversely, when the temperature decreases, their capacitance increases.
The change in capacitance due to temperature can be expressed as a percentage change per degree Celsius (°C) of temperature change. For example, a capacitor with a temperature coefficient of +200 ppm/°C will increase its capacitance by 0.02% for every degree Celsius increase in temperature.
It's important to note that while some capacitors are designed to minimize the temperature coefficient of capacitance, it's challenging to completely eliminate this effect. Temperature variations can cause shifts in the values of capacitors, which may impact the performance of the RC circuit, especially in precision applications.
When designing circuits that are sensitive to temperature changes, engineers may choose capacitors with low temperature coefficients or use compensation techniques to mitigate the impact of temperature variations.