## Technical Handbook | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

## Capacitors 1 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

## Capacitors and Capacitance |
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## Reversible Electrolytic Capacitors | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

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## Metallized Film Capacitors | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

## A Brief History of CapacitanceThe unit of capacitance is the Farad (symbol Algebraically, capacitance is usually represented as 'C'.
## Units of CapacitanceThe unit of capacitance is the
## Capacitors Connected in ParallelConnecting capacitors in parallel results in a total capacitance which is the sum of the two capacitors - so connecting two 5µF in parallel gives a total capacitance of 10µF; 1µF in parallel with 4.7µF results in 5.7µF.
There is also a slight reduction in The combined voltage rating will be equivalent to the lower rated of the two capacitors. ## Capacitors Connected in SeriesNot normally recommended. For situations where such connection is unavoidable, the combined capacitance may be calculated as:
DF will approximate to the higher of the two values and ripple current will be equivalent to the lower of the two values.The combined voltage rating will be equivalent to the lower rated of the two capacitors.
## AC and DC Voltage RelationshipsThe numerical relations of a sine wave are
For practical applications using reversible electrolytics it is generally sufficient to derive an AC working voltage from the stated DC voltage using the rms value; so a 50V DC rating could be accepted as equivalent to 35V AC (50 x 0.707 = 35.35). This holds true up to about 5KHz. At high frequencies (RF) considerable derating is required, as losses increase and heating results.
**These are theoretical equivalents, and should be used only as a guide. In practical applications, other parameters may intrude.****Regardless of its AC rating, no capacitor should ever be connected to mains circuits unless it is expressly stated as being suitable for mains applications.**
## Ripple CurrentRipple current is a parameter which, in practice, only applies to electrolytic capacitors. It represents the AC signal element in a voltage with a DC offset as would be seen by a conventional polar electrolytic capacitor. In the case of reversible electrolytics used in loudspeaker crossover circuits, where there is no DC offset voltage, it follows that ripple current will be identical to the AC current passed by the capacitor. The effective series resistance ( With film capacitors, and especially polypropylene film types, the ESR is so small that there is virtually no heat build up even at very high currents - far higher than should be found in a loudspeaker crossover.
## Dissipation Factor and 'Q'Some people prefer to discuss the dissipation factor of a capacitor in terms of 'Q' - probably to parallel the concept as correctly applied to inductors. Q is defined as the reciprocal of DF - thus the higher the Q, the 'better' the capacitor and the lower the dissipation factor. See also
## Matching Capacitor Type to ApplicationOf the wide range of available capacitor types, those particulary applicable to audio may be divided into two main categories: The type of capacitor to be used in a given application may usually be decided in terms of working voltage versus dissipation factor. In general, the lower the dissipation factor, the better the signal transmission, i.e. the better the perceived audio performance. The following graph displays the relative merits of the various capacitor types available from ECL. |