Charge And Capacitors
types of capacitors:
There are many different types of capacitors that have different properties.
Electrolytic.Electrolytic capacitors are polarised. This means that they have a positive and a negative electrode, usually made out of Aluminium. If the current to the capacitor is reversed, the capacitor will not work or could blow. The Electrolytic capacitor can have axial electrodes. This means that instead of the electrodes exiting the capacitor at the bottom, they have one at the top and one at the bottom. Usually have a value in micro-farads normally ranging from one micro-farad to thousands of micro-farads. The aluminium electrolytic capacitor is usually used as a filter to bypass low frequency signals but cannot be used for high frequency signals.
Tantalum capacitors are electrolytic capacitors that use a material called tantalum for the electrodes instead of aluminium. Large values of capacitance can be obtained like the aluminium capacitor but are superior to aluminium electrolytic capacitors in both temperature and frequency characteristics and can be used for analogue signal circuits.
Ceramic capacitors have no polarity and are commonly used for high frequency circuits because they are not constructed as a coil internally, but the ceramic capacitor cannot be used for analogue signals as the capacitor distorts the signal.
In these capacitors, a polystyrene film is used as the dielectric material. These capacitors cannot be used in high frequency circuits due to their coil like structure but are used in filter circuits or timing circuits. These capacitors do not have a certain polarity
Polyester film capacitors.
These capacitors use a film of polyester as the dielectric material and have no polarity. These capacitors have a low tolerance but are cheap.
Polypropylene capacitors are normally used when a higher tolerance is needed that is too high for the polyester capacitor. These capacitors have no polarity.
Mica capacitors have a good stability because their temperature coefficient is small. Because their frequency characteristics are good, they are normally used in resonance circuits and high frequency filters. The mica capacitors can also be used for high voltage applications due to their good insulation but they are fairly expensive.