What is the definition of good

The quality Q for components

For the example of the coil, it makes sense to relate the series resistance of the coil to the inductance. This leads indirectly to the concept of goodness:


Definition: The goodness (Q) a coil or a capacitor that is Ratio of reactive power to active power in this component, so:


From this simple definition one can calculate the quality for 4 different arrangements. See table 7 for this.

In parallel to the definition of quality, the literature also includes the definition of Loss angle δ.


As can be easily shown, there is a relationship between loss angle and goodness:



Table 7: Calculation of the quality for different arrangements




Coil with parallel resistance


Coil with series resistance


Capacitor with parallel resistance


Series resistor capacitor



anecdote: The formula abbreviation Q for goodness is borrowed from American vocabulary. Originally, quality was introduced there as a "quality factor". However, the term quality was later defined differently in production technology. The quality of a component is the number of components delivered divided by the number of defective components delivered. For passive SMD components, a quality in the order of 10 is achieved today5. In the absence of an alternative to Quality, American literature today calls it Q designated. This is considered to be a word made up of a single consonant.