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About:
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Capacitor
A capacitor ;is a device that stores electrical energy in an electric field. It is a passive electronic component with two terminals.
The effect of a capacitor is known as capacitance. While some capacitance exists between any two electrical conductors in proximity in a circuit, a capacitor is a component designed to add capacitance to a circuit. The capacitor was originally known as a condenser or condensation.
The physical form and construction of practical capacitors vary widely and many types of capacitors are in common use. Most capacitors contain at least two electrical conductors often in the form of metallic plates or surfaces separated by a dielectric medium. A conductor may be a foil, thin film, sintered bead of metal, or an electrolyte. The nonconducting dielectric acts to increase the capacitor's charge capacity. Materials commonly used as dielectrics include glass, ceramic, plastic film, paper, mica, air, and oxide layers. Capacitors are widely used as parts of electrical circuits in many common electrical devices. Unlike a resistor, an ideal capacitor does not dissipate energy, although real-life capacitors do dissipate a small amount (see Non-ideal behavior). When an electric potential difference (a voltage) is applied across the terminals of a capacitor, for example when a capacitor is connected across a battery, an electric field develops across the dielectric, causing a net positive charge to collect on one plate and net negative charge to collect on the other plate. No current actually flows through the dielectric. However, there is a flow of charge through the source circuit. If the condition is maintained sufficiently long, the current through the source circuit ceases. If a time-varying voltage is applied across the leads of the capacitor, the source experiences an ongoing current due to the charging and discharging cycles of the capacitor.
What are ceramic capacitors?
A ceramic capacitor uses a ceramic material as the dielectric. Ceramics were one of the first materials to be used in the production of capacitors, as it was a known insulator. Many geometries were used in ceramic capacitors, of which some, like ceramic tubular capacitors and barrier layer capacitors, are obsolete today due to their size, parasitic effects, or electrical characteristics. The types of ceramic capacitors most often used in modern electronics are the multi-layer ceramic capacitor, otherwise named ceramic multi-layer chip capacitor (MLCC), and the ceramic disc capacitor. MLCCs are the most produced capacitors with a quantity of approximately 1000 billion devices per year. They are made in SMD (surface-mounted) technology and are widely used due to their small size. Ceramic capacitors are usually made with very small capacitance values, typically between 1nF and 1μF, although values up to 100μF are possible. Ceramic capacitors are also very small in size and have a low maximum rated voltage. They are not polarized, which means that they may be safely connected to an AC source. Ceramic capacitors have a great frequency response due to low parasitic effects such as resistance or inductance.
Characteristics
Precision and tolerances
There are two classes of ceramic capacitors available today: class 1 and class 2. Class 1 ceramic capacitors are used where high stability and low losses are required. They are very accurate and the capacitance value is stable in regard to the applied voltage, temperature, and frequency. The NP0 series of capacitors has a capacitance thermal stability of ; ±0.54% within the total temperature range of -55 to +125 °C. Tolerances of the nominal capacitance value can be as low as 1%.
Class 2 capacitors have a high capacitance per volume and are used for less sensitive applications. Their thermal stability is typically ±15% in the operating temperature range, and the nominal value tolerances are around 20%.
Size advantages
When high component packing densities are required, as is the case in most modern printed circuit boards (PCBs), MLCC devices offer a great advantage compared to other capacitors. To illustrate this point, the “0402 multi-layer ceramic capacitor package measures just 0.4 mm x 0.2 mm. In such a package, there are 500 or more ceramic and metal layers. The minimum ceramic thickness as of 2010 is on the order of 0.5 microns.
High voltage and high power
Physically larger ceramic capacitors can be made to withstand much higher voltages and these are called power ceramic capacitors. These are physically much larger than those used on PCBs and have specialized terminals for safe connection to a high voltage supply. Power ceramic capacitors can be made to withstand voltages in the range of 2kV up to 100 kV, with a power specified at much higher than 200 volt-amperes.
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