Capacitors

What is a capacitor and what does it do?

A capacitor is a device used to store energy as an electric charge, similar to a battery but they are able to release the charge much faster. The amount it's able to store is known as capacitance, this is measured in Farads (F). They comprise 2 metal plates (conductors) separated by an electrical insulator (dielectric).

What capacitor types are available?

There are many different types available with detailed specifications for their required function. The main elements are available in varying materials and these determine many properties of the capacitor. Some factors to consider are:

• Metal plate material - e.g silver, tantalum, aluminium
• Dielectric plate material - paper, film, ceramic, glass
• Max voltage - cannot be exceeded or the device will break
• Size - capacitance and dimensions
• Tolerance - variance on the capacitance value
• Mounting type - how it is fixed to the circuit
• ESR (Equivalent series resistance) - resistance of the terminals

Applications of capacitors

Capacitors are found all around us, they are used in most electronics from fans to hybrid electric cars - there are over 500 just in a typical smartphone. Here are some of their uses:

• Decoupling capacitors - can control high-frequency noise, removing voltage ripples from the power supply.
• Energy storage and supply - deliver stored energy bursts quickly, like a camera flash for example.
• Signal filtering - they are able to block low-frequency signals and allow higher-frequencies to pass through. Useful in telecommunications.