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Capacitors

Capacitors are one of the basic building blocks of an electronic circuit. In simplistic terms, they are constructed from two metallic plates separated by an insulator known as a dielectric. The dielectric must be made from nonconductive material so that it opposes the flow of electricity.

As a current is applied, one of the metallic plates will become positively charged and the other negatively charged, the charge remaining in place until such time as the current is removed. When power is required, the circuit can be switched to conduct current between the two plates, and the capacitor is able to release its charge. This is called the discharge.

Capacitors therefore act like miniature batteries that are capable of charging and discharging very quickly, analogous to the energy stored by a coiled spring. As a result capacitors are therefore used to regulate power as well as for smoothing and conditioning signals.

There are a number of different types of capacitors, some of the most common forms are listed below:-

Ceramic Capacitors

have a thin outer shell and are ideal for low cost applications. They offer stable low capacitance at low voltages. These capacitors can be heat sensitive leading to their destruction if the capacitor is used for the wrong application. They do not have designated anode or cathode leads unlike electrolytic capacitors. As a result they can have the positive or negative charges on either lead.

Electrolytic Capacitors

are also a low cost component. They are sometimes inserted to PCB assemblies using a radial insertion process. They can be differentiated from ceramic capacitors because they have polarity and have a positive anode and a negative cathode. The cathode is indicated by a white line with arrows on the outer skin of the capacitor body. These capacitors are used for lower voltages and capacitance.

Tantalum Capacitors

are a type of electrolytic capacitor. They are made from tantalum metal. The metal, in a 'capsule of powder' acts as one plate, its protective oxide layer the dielectric, the second plate being made from an electrolytic solution into which the metal powder is suspended. This type of capacitor can store a lot of charge relative to its mass. This has enabled electronic designers to use this type of capacitor where size and weight characteristics are very important. As a result tantalum capacitors are used widely in mobile telecommunications, PDAs, laptop computers and other portable electronic hardware.

Passives Topics

Capacitors

Resistors

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Guide Written by Paul Wilson

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