A capacitor (originally known as condenser) is a passive two-terminal electrical component used to store energy in an electric field. in Wikipedia

Os formatos típicos consistem em dois eletrodos ou placas que armazenam cargas opostas. Estas duas placas são condutoras e são separadas por um isolante ou por um dieléctrico. A carga é armazenada na superfície das placas, no limite com o dieléctrico. Devido ao fato de cada placa armazenar cargas iguais, porém opostas, a carga total no dispositivo é sempre zero.

in Wikipedia


Capacitors in parallel:

um diagrama com vários capacitores, lado a lado, cada qual com a ponta correspondente conectada aos mesmos fios
 C_{eq} = C_1  + C_2 + \cdots + C_n \,\!

Capacitors in series

Um diagrama com vários capacitores, conectados pelas pontas, em seqüência, com a mesma quantidade de corrente atravessando cada um
 \frac{1}{C_{eq}} = \frac{1}{C_1} + \frac{1}{C_2} + \cdots +  \frac{1}{C_n}

Most commun

Tolerances around de 5 % ou 10 %.

Condensares are often categorized according to the material used as the dielectric. The following types of dielectric are used:

ceramic (low values ​​up to about 1 mF)

C0G or NP0 – typically 4.7 pF to 0.047 pF, 5%. High tolerance and temperature performance. Larger and more expensive

X7R – typically 3300 pF to 0.33 uF, 10%. Good for coupling non-critical applications with timer.

Z5U – typically from 0.01 pF to 2.2 pF, 20%. Good for applications or bypass couplings. Low price and small size.

polystyrene (usually in the range of picofarades)
polyester (from about 1 nF to 1 million mF)
polypropylene (low loss. high voltage resistant faults)
tantalum (compact, low-voltage device, up to approximately 100 mF)
electrolytic (high power, compact but with much loss, in the range of 1 mF to 1000 mF)

Important properties of capacitors, in addition to its capacitance, are the maximum working voltage and the amount of energy lost in the dielectric. Capacitors for high power and maximum current Equivalent Series Resistance in (ESR) are further considerations. A typical for most ESR of the capacitors is between 0.0001 and 0.01 ohm ohm, preferred low values ​​for high current applications.

Since capacitors have such low ESRs, they have the ability to deliver huge currents into short circuits, which can be dangerous. For safety, all large capacitors should be discharged before handling. This is done by placing a small resistor of 1 ohm to 10 ohm terminals, that is, creating a circuit between the terminals passing through the resistor.

Capacitors can also be manufactured on electrical semiconductor integrated circuits using metallic lines and insulators on a substrate. These capacitors are used to store analog signals switched by capacitors for filters, and to store digital data in dynamic random access memory (DRAM). Unlike discrete capacitors, however, most of the manufacturing process, precise tolerances are not possible (15% to 20% is considered good).

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