Capacitors
Capacitors
Capacitors are a passive electrical component with two terminals that store electromagnetic energy in the form of an electric field. Terminals are connected to two conductive plates that have a dielectric material between them. They store an electric charge on their conductive plates. The charged plates separated by the dielectric material create an electric field. Capacitance is a parameter of a capacitor that indicates the amount of stored electric charge for a given voltage applied to its terminals. It is measured in farads (F). For example, doubling the capacitance will double stored electric charge (for a given constant voltage at terminals). Capacitors are classified based on physical materials used for three-layer conductor-dielectric-conductor structure. For example, those with metal-dielectric-electrolyte materials are called electrolytic capacitors; metal-ceramic-metal are called ceramic capacitors, etc. Those that are non-polarized may be connected either to positive or negative voltage. If they are polarized they must be connected to a positive voltage, with the positive terminal being marked on the packaging.
Chip tantalum capacitor
A tantalum electrolytic capacitor is an electrolytic capacitor, a passive component of electronic circuits. It consists of a pellet of porous tantalum metal as an anode, covered by an insulating oxide layer that forms the dielectric, surrounded by liquid or solid electrolyte as a cathode. Because of its very thin and relatively high permittivity dielectric layer, the tantalum capacitor distinguishes itself from other conventional and electrolytic capacitors in having high capacitance per volume (high volumetric efficiency) and lower weight. Tantalum is a conflict mineral. Tantalum electrolytic capacitors are considerably more expensive than comparable aluminum electrolytic capacitors. Tantalum capacitors are inherently polarized components. Reverse voltage can destroy the capacitor. Non-polar or bipolar tantalum capacitors are made by effectively connecting two polarized capacitors in series, with the anodes oriented in opposite directions.
Ceramic capacitor
A ceramic capacitor is a fixed-value capacitor where the ceramic material acts as the dielectric. It is constructed of two or more alternating layers of ceramic and a metal layer acting as the electrodes. The composition of the ceramic material defines the electrical behavior and therefore applications. Ceramic capacitors are divided into two application classes: Class 1 ceramic capacitors offer high stability and low losses for resonant circuit applications. Class 2 ceramic capacitors offer high volumetric efficiency for buffer, by-pass, and coupling applications. Ceramic capacitors, especially multilayer ceramic capacitors (MLCCs), are the most produced and used capacitors in electronic equipment that incorporate approximately one trillion (1012) pieces per year.[1] Ceramic capacitors of special shapes and styles are used as capacitors for RFI/EMI suppression, as feed-through capacitors and in larger dimensions as power capacitors for transmitters.
Aluminum electrolytic capacitors
Aluminum electrolytic capacitors are polarized electrolytic capacitors whose anode electrode (+) is made of a pure aluminum foil with an etched surface. The aluminum forms a very thin insulating layer of aluminum oxide by anodization that acts as the dielectric of the capacitor. A non-solid electrolyte covers the rough surface of the oxide layer, serving in principle as the second electrode (cathode) (-) of the capacitor. A second aluminum foil called "cathode foil" contacts the electrolyte and serves as the electrical connection to the negative terminal of the capacitor. Aluminum electrolytic capacitors are divided into three subfamilies by electrolyte type: non-solid (liquid, wet) aluminum electrolytic capacitors, solid manganese dioxide aluminum electrolytic capacitors, and solid polymer aluminum electrolytic capacitors. Aluminum electrolytic capacitors with non-solid electrolyte are the most inexpensive type and also those with widest range of sizes, capacitance and voltage values. They are made with capacitance values from 0.1 μF up to 2,700,000 μF (2.7 F),[1] and voltage ratings ranging from 4 V up to 630 V.[2] The liquid electrolyte provides oxygen for re-forming or "self-healing" of the dielectric oxide layer. However, it can evaporate through a temperature-dependent drying-out process, which causes electrical parameters to drift, limiting the service life time of the capacitors. Due to their relatively high capacitance values aluminum electrolytic capacitors have low impedance values even at lower frequencies like mains frequency. They are typically used in power supplies, switched-mode power supplies and DC-DC converters for smoothing and buffering rectified DC voltages in many electronic devices as well as in industrial power supplies and frequency converters as DC link capacitors for drives, inverters for photovoltaic, and converters in wind power plants. Special types are used for energy storage, for example in photoflash or strobe applications or for signal coupling in audio applications. Aluminum electrolytic capacitors are polarized capacitors because of their anodization principle. They can only be operated with DC voltage applied with the correct polarity. Operating the capacitor with wrong polarity or with AC voltage leads to a short circuit and can destroy the component. The exceptions is the bipolar aluminum electrolytic capacitor, which has a back-to-back configuration of two anodes in one case and can be used in AC applications.
Film Capacitors
Film capacitors, plastic film capacitors, film dielectric capacitors, or polymer film capacitors, generically called film caps as well as power film capacitors, are electrical capacitors with an insulating plastic film as the dielectric, sometimes combined with paper as carrier of the electrodes. The dielectric films, depending on the desired dielectric strength, are drawn in a special process to an extremely thin thickness, and are then provided with electrodes. The electrodes of film capacitors may be metallized aluminum or zinc applied directly to the surface of the plastic film, or a separate metallic foil. Two of these conductive layers are wound into a cylinder-shaped winding, usually flattened to reduce mounting space requirements on a printed circuit board, or layered as multiple single layers stacked together, to form a capacitor body. Film capacitors, together with ceramic capacitors and electrolytic capacitors, are the most common capacitor types for use in electronic equipment, and are used in many AC and DC microelectronics and electronics circuits.[1] A related component type is the power (film) capacitor. Although the materials and construction techniques used for large power film capacitors are very similar to those used for ordinary film capacitors, capacitors with high to very high power ratings for applications in power systems and electrical installations are often classified separately, for historical reasons. As modern electronic equipment gained the capacity to handle power levels that were previously the exclusive domain of "electrical power" components, the distinction between the "electronic" and "electrical" power ratings has become less distinct. In the past, the boundary between these two families was approximately at a reactive power of 200 volt-amperes, but modern power electronics can handle increasing power levels.
Mica Capacitors
Mica has been used as a capacitor dielectric since the mid-19th century. William Dubilier invented a small mica capacitor in 1909 which was used in decoupling applications.They were put into large scale commercial production to meet military requirements in World War I. Mica is less prone to crack under mechanical shock than glass, a useful property for equipment subject to shellfire. Like glass, mica has a substantially higher permittivity than paper so capacitors can be made smaller. In 1920 Dubilier developed a capacitor consisting of a flaked sheet of mica coated on both sides with silver. He formed the Dubilier Condenser Company to manufacture them. Ceramic capacitors were also used in the 1920s due to a shortage of mica, but by the 1950s silver mica had become the capacitor of choice for small-value RF applications.This remained the case until the latter part of the 20th century when advances in ceramic capacitors led to the replacement of mica with ceramic in most applications.