Aluminum is used for the electrodes by using a thin oxidization membrane.
Large values of capacitance can be obtained in comparison with the size of the capacitor, because the dielectric used is very thin. The most important characteristic of electrolytic capacitors is that they have polarity,this means that it is very important which way round they are connected ,or it will burst. Make absolutely no mistakes. Generally, in the circuit diagram, the positive side is indicated by a "+" (plus) symbol.
Electrolytic capacitors range in value from about 1µF to thousands of µF. Mainly this type of capacitor is used as a ripple filter in a power supply circuit, or as a filter to bypass low frequency signals, etc. Because this type of capacitor is comparatively similar to the nature of a coil in construction, it isn't possible to use for high-frequency circuits.
Fig(6) Electrolytic Capacitors
2.2.2. Tantalum Capacitors
Tantalum Capacitors are electrolytic capacitors that are use a material called tantalum for the electrodes. Large values of capacitance similar to aluminum electrolytic capacitors can be obtained. Also, tantalum capacitors are superior to aluminum electrolytic capacitors in temperature and frequency characteristics. When tantalum powder is baked in order to solidify it, a crack forms inside. An electric charge can be stored on this crack.
These capacitors have polarity as well. Usually, the "+" symbol is used to show the positive component lead. Capacitance can change with temperature as well as frequency, and these types are very stable. Therefore, tantalum capacitors are used for circuits which demand high stability in the capacitance values. Also, it is said to be common sense to use tantalum capacitors for analog signal systems, because the current-spike noise that occurs with aluminum electrolytic capacitors does not appear.
The "+" symbol is used to show the positive lead
2.2.3. Ceramic Capacitors
Ceramic capacitors are constructed with materials such as titanium acid barium used as the dielectric. Internally, these capacitors are not constructed as a coil, so they can be used in high frequency applications. Typically, they are used in circuits which bypass high frequency signals to ground.
Fig (8) Ceramic Capacitors
These capacitors have the shape of a disk. Their capacitance is comparatively small.
2.2.4. Multilayer Ceramic Capacitors
The multilayer ceramic capacitor has a many-layered dielectric. These capacitors are small in size, and have good temperature and frequency characteristics.Square wave signals used in digital circuits can have a comparatively high frequency component included. This capacitor is used to bypass the high frequency to ground.
Fig (9) Multilayer Ceramic Capacitors
2.2.5. Polystyrene Film Capacitors
In these devices, polystyrene film is used as the dielectric. This type of capacitor is not for use in high frequency circuits, because they are constructed like a coil inside. They are used well in filter circuits or timing circuits which run at several hundred KHz or less.
Fig (10) Polystyrene Film Capacitors
2.2.6. Electric Double Layer Capacitors (Super Capacitors)
This is a "Super Capacitor," which is quite a wonder.The capacitance is 0.47 F (470,000 µF). Care must be taken when using a capacitor with such a large capacitance in power supply circuits, etc. The rectifier in the circuit can be destroyed by a huge rush of current when the capacitor is empty.
Fig(11) Super Capacitors
For a brief moment, the capacitor is more like a short circuit. A protection circuit needs to be set up.
2.2.7. Polyester Film Capacitors
This capacitor uses thin polyester film as the dielectric. They are not high tolerance, but they are cheap and handy. Their tolerance is about ±5% to ±10%.These capacitors have no polarity. .
Fig (12) Polyester Film Capacitors
2.2.8. Polypropylene Capacitors
This capacitor is used when a higher tolerance is necessary than polyester capacitors offer. Polypropylene film is used for the dielectric. It is said that there is almost no change of capacitance in these devices if they are used with frequencies of 100KHz or less. The pictured capacitors have a tolerance of ±1%.
Fig (13) Polypropylene Capacitors
2.2.9. Mica Capacitors
These capacitors use Mica (which is) for the dielectric. Mica capacitors have good stability because their temperature coefficient is small. Because their frequency characteristic is excellent, they are used for resonance circuits, and high frequency filters. Also, they have good insulation, and so can be utilized in high voltage circuits. It was often used for vacuum tube style radio transmitters, etc. Mica capacitors do not have high values of capacitance, and they can be relatively expensive. Pictured at the right are "Dipped mica capacitors." These can handle up to 500 volts. These capacitors have no polarity.
Fig (14) Mica Capacitors
2.2.10. Metalized Polyester Film Capacitors
These capacitors are a kind of a polyester film capacitor. Because their electrodes are thin, they can be miniaturized. These capacitors have no polarity.
Fig (15) Metalized Polyester Film Capacitors
