Variety of capacitors available in market, some times I discover alien components on PCBs from Big companies. Some are don’t look like capacitors. Some are specific to some unique job, if u replace with another one it may not work at all like the low ESR capacitors in DC DC converters.

 

Ceramic

A ceramic capacitor is a two-terminal non-polar device. The classical ceramic capacitor is the “disc capacitor”. This device pre-dates the transistor and was used extensively in vacuum-tube equipment (e.g., radio receivers) from about 1930 through the 1950s, and in discrete transistor equipment from the 1950s through the 1980s. As of 2007, ceramic disc capacitors are in widespread use in electronic equipment, providing high capacity and small size at low price compared to other low value capacitor types.

Multilayer ceramic capacitors are increasingly used to replace tantalum and low capacitance aluminium electrolytic capacitors in applications such as bypass or high frequency switched-mode power supplies as their cost, reliability and size becomes competitive. In many applications, their low ESR allows the use of a lower nominal capacitance value

 

Electrolytic

An electrolytic capacitor is a type of capacitor that uses an electrolyte (an ionic conducting liquid) as one of its plates to achieve a larger capacitance per unit volume than other types, but with performance disadvantages. All capacitors conduct alternating current (AC) and block direct current (DC) and can be used, amongst other applications, to couple circuit blocks allowing AC signals to be transferred while blocking DC power, to store energy, and to filter signals according to their frequency. The large capacitance of electrolytic capacitors makes them particularly suitable for passing or bypassing low-frequency signals and storing large amounts of energy. They are widely used in power supplies and for decoupling unwanted AC components from DC power connections.

Aluminum electrolytic capacitors are constructed from two conducting aluminum foils, one of which is coated with an insulating oxide layer, and a paper spacer soaked in electrolyte. The foil insulated by the oxide layer is the anode while the liquid electrolyte and the second foil acts as the cathode. This stack is then rolled up, fitted with pin connectors and placed in a cylindrical aluminum casing. The two most popular geometries are axial leads coming from the center of each circular face of the cylinder, or two radial leads or lugs on one of the circular faces.

 

Polyester film

This capacitor uses a thin polyester film as a dielectric. Not as high a tolerance as polypropylene, but cheap and handy, temperature stable, readily available, widely used. Tolerance is approx 5% to 10%. Can be quite large depending on capacity or rated voltage and so may not be suitable for all applications. Temperature stability is poorer than paper capacitors. Usable at low (AC power) frequencies, but inappropriate for RF applications due to excessive dielectric heating.

 

 

 

 

 

 

Tantalum Capacitors

 

Tantalum capacitors are polarised and have low voltage ratings like electrolytic capacitors. They are expensive but very small so they are used where a large capacitance is needed in a small size such as mobile phones or laptop computers. These capacitors have increasingly become an important as the demand for ever smaller electronic gadgets has grown. Columbite-tantalite – coltan, for short, the ore from which tantalum is refined is mined in Australia, Egpyt. The high demand for the ore has also financed civil wars in the Democratic Republic of the Congo. A UN security council report charged that a great deal of the ore is mined illegally and smuggled over the country’s eastern borders by militas from neighbouring Uganda, Burundi and Rwanda providing the revenue to finance the military occupation of the Congo.

 

Metalized Polyster Film

No polarity, dielectric made of Polyester or DuPont trade name “Mylar”. Good quality, low drift, temperature stable. Because the electrodes are thin they can be made very very small. Good all-round capacitor.Care is necessary, because the component lead easily breaks off from these capacitors. Once lead has come off, there is no way to fix it. It must be discarded.

 

 

 

 

Polystyrene capacitors

 

No polarity, is used as a dielectric. Constructed like a coil inside so not suitable for high frequency applications. Well used in filter circuits or timing applications using a couple hundred KHz or less. Electrodes may be reddish of color because of copper leaf used or silver when aluminum foil is used for electrodes.

Excellent general purpose plastic film capacitor. Excellent stability, low moisture pick-up and a slightly negative temperature coefficient that can be used to match the positive temperature co-efficient of other components. Ideal for low power RF and precision analog applications

 

 

 

 

 

 

MICA Capacitors

This type is an extremely accurate device with very low leakage currents. It is constructed with alternate layers of metal foil and mica insulation, stacked and encapsulated. These capacitors have small capacitances and are often used in high frequency circuits (eg. : RF circuits). They are very stable under variable voltage and temperature conditions. Tolerances range from +/-0.25 to +/-5 percent. Capacitances range from 1 pf to 0.01 uF, with maximum voltage ratings from 100 V to 2.5 k

About ASIM MAHAKUL

Hello, I am Asim admin of this blog. An expert in Scientific Instrumentation (Analytical Instrumentation). My works are always associated with both Physics and electronics. Currently working on ARM based embedded systems for Optical(UV and Visible) and electrochemical spectroscopy (EIS). My M.Tech. Thesis was related to all these things. I had worked for a 8 bit microcontroller based standalone EIS (electrical impedance spectroscopy) device. I have Masters in Instrumentation engineering from NIT Kurukshetra,Haryana and Masters in Electronics Science from Sambalpur University, Odisha (Formerly Orissa/Utkal) Am also work for PHP MySQL AJAX based CMS design. i love blogging and coding(am not an expert).

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