This tool calculates the Quality Factor of a Capacitor. As the name suggests the higher the numerical value, the better the quality of the component.
Formula
Q = 1/(2π*f*C*ESR)
where,
- f = Frequency
- C = Capacitance
- ESR = Equivalent Series Resistance
The Dissipation Factor DF = 1/Q.
Background
The quality factor Q, is a dimensionless number that is equal to the capacitor’s reactance divided by the capacitor’s equivalent series resistance (ESR).
Q = XC/ESR
An ideal capacitor has an ESR = 0. In that case Q = ∞. However in practice the series resistance is never zero. Ideally this value is kept as small as possible to minimize losses.
Typical quality factor values of a Capacitor advertised as having High Q are shown below.
Using the calculator above, a capacitance of 1000 pF, Frequency 1 kHz and ESR of around 16 Ω gives a Q = 10,000.
The picture below shows Q vs Capacitance of a 1000 pF capacitor intended for RF applications.
For a fixed value of capacitance:
- Q decreases with increasing frequency
- ESR increases with frequency.
Example Calculation
A capacitor with an ESR of 0.2 Ω, capacitance 10 μF and Frequency 120 Hz has a Quality Factor Q = 663.
Summary
The Quality Factor (Q) of a Capacitor refers to its ability to store and release energy efficiently.
It is a measure of the ratio between the maximum energy stored in the capacitor and the energy dissipated per cycle.
Q is determined by various factors such as the capacitance, reactance, and operating frequency of the circuit. A higher Q signifies a more efficient capacitor. In an ideal capacitor, Q would be infinite, meaning that no energy is dissipated during operation.
However, in practical capacitors, energy dissipation is inevitable due to factors such as internal resistance and dielectric losses.
Book Recommendation
Interested in learning more about Electronics?
We recommend checking out the Art of Electronics.
