Why are different types of capacitors used in various circuits?

Electronic experimenters often wonder why specific types of non-polarized capacitors are specified or used in different circuit types and whether substituting one type for another will make any difference.

The short answer is yes; a specific type can be the most attractive choice in an application because its characteristics fit the type of circuit it’s being used in. Cost aside, there is no best overall type of capacitor to use in all applications.

The longer answer is that a particular type of capacitor may best suit the most important characteristic that circuit requires of that capacitor. For example, in LC oscillator circuits, frequency stability is typically an important attribute for the designer. For a similar situation in which the LC circuit is being used in a filter section, the Q factor may be the most important feature for the circuit designer.

Along with cost, the long-term stability, temperature range stability (coefficient), Q factor, voltage coefficient, and value tolerance attributes of each type of capacitor technology varies considerably. Consulting manufacturer data sheets can help you choose which type or types are the best fit for you application. Below are some common types and why one might choose them.

Ceramic (NPO) – Best temperature stability, tight tolerances

Silver Mica – High Q/ high voltage range stability

Polystyrene – High insulation/Low leakage

Polypropylene Film – low self inductance and high tolerance

Polycarbonate – High dielectric strength (breakdown voltage)

Mylar Film – Low cost

These are of course just some of the reasons you might choose one of the above types, but availability and cost are often very important qualities to consider in any choice you make.

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