NationMaster - Encyclopedia: Capacitor (component)

Practical capacitors are often classified according to the material used as the dielectric with the dielectrics divided into two broad categories: bulk insulators and metal-oxide films (so-called electrolytic capacitors).

1 Capacitor construction
2 Types of dielectric
3 Fixed capacitor comparisons
4 Variable capacitors
5 Non-ideal properties of practical capacitors
6 Component values and identification
- 6.1 Standard values
- 6.2 Colour coding
7 See also
8 References

Capacitor construction

Structure of a surface mount (SMT) film capacitor.

Capacitors have thin conducting plates (usually made of metal), separated by a layer of dielectric, then stacked or rolled to form a compact device. Image File history File links Capacitor. ... Image File history File links Capacitor. ...

Many types of capacitor are available commercially, with capacitances ranging from the picofarad range to more than a farad, and voltage ratings up to hundreds of kilovolts. In general, the higher the capacitance and voltage rating, the larger the physical size of the capacitor and the higher the cost. Tolerances in capacitance value for discrete capacitors are usually specified as a percentage of the nominal value. Tolerances ranging from 50% (electrolytic types) to less than 1% are commonly available. The cross of the war memorial and a menorah for Hanukkah coexist in Oxford. ...

Another figure of merit for capacitors is stability with respect to time and temperature, sometimes called drift. Variable capacitors are generally less stable than fixed types.

The electrodes need round edges to avoid field emission. Air has low breakdown voltage, so any air inside a capacitor - especially at plate edges - will reduce the voltage rating. Even closed air bubbles in the insulator or between the insulator and the electrode lead to gas discharge, particularly in AC or High Frequency applications. Groups of identically constructed capacitor elements are often connected in series for operation at higher voltage. Also known as Fowler-Nordheim tunneling, field emission is a form of quantum tunneling in which electrons pass through a barrier in the presence of a high electric field. ... -1... Look up AC, ac in Wiktionary, the free dictionary. ... High frequency (HF) radio frequencies are between 3 and 30 MHz. ...

Types of dielectric





Capacitor	Polarized Capacitor	Variable Capacitor

Capacitor symbols

Air-gap: An air-gap capacitor has a low dielectric loss. Large-valued, tunable capacitors that can be used for resonating HF antennas can be made this way.
Ceramic: The main differences between ceramic dielectric types are the temperature coefficient of capacitance, and the dielectric loss. C0G and NP0 (negative-positive-zero, i.e. ±0) dielectrics have the lowest losses, and are used in filters, as timing elements, and for balancing crystal oscillators. Ceramic capacitors tend to have low inductance because of their small size. NP0 refers to the shape of the capacitor's temperature coefficient graph (how much the capacitance changes with temperature). NP0 means that the graph is flat and the device is not affected by temperature changes.
- C0G or NP0 — Typically 4.7 pF to 0.047 µF, 5%. High tolerance and temperature performance. Larger and more expensive.
- X7R — Typical 3300 pF to 0.33 µF, 10%. Good for non-critical coupling, timing applications. Subject to microphonics.
- Z5U or 2E6 — Typical 0.01 µF to 2.2 µF, 20%. Good for bypass, coupling applications. Low price and small size. Subject to microphonics.
- Ceramic chip: 1% accurate, values up to about 1 µF, typically made from Lead zirconate titanate (PZT) ferroelectric ceramic
Glass — used to form extremely stable, reliable capacitors.
Paper — common in antique radio equipment, paper dielectric and aluminum foil layers rolled into a cylinder and sealed with wax. Low values up to a few μF, working voltage up to several hundred volts, oil-impregnated bathtub types to 5,000 V used for motor starting and high-voltage power supplies, and up to 25,000 V for large oil-impregnated energy discharge types.
Polycarbonate good for filters, low tempco, good aging, expensive
Polyester, (PET film): (from about 1 nF to 1 μF) signal capacitors, integrators.
Polystyrene: (usually in the picofarad range) stable signal capacitors.
Polypropylene: low-loss, high voltage, resistant to breakdown, signal capacitors.
PTFE or Teflon ™: higher performing and more expensive than other plastic dielectrics.
Silvered mica: These are fast and stable for HF and low VHF RF circuits, but expensive.
Electrolytic capacitors have a larger capacitance per unit volume than other types, making them valuable in relatively high-current and low-frequency electrical circuits, e.g. in power-supply filters or as coupling capacitors in audio amplifiers. High-capacity electrolytics, also known as supercapacitors or ultracapacitors, have applications similar to those of rechargable batteries, e.g. in electrically powered vehicles;
Printed circuit board: Metal conductive areas in different layers of a multi-layer printed circuit board can act as a highly stable capacitor. It is common industry practice to fill unused areas of one PCB layer with the ground conductor and another layer with the power conductor, forming a large distributed capacitor between the layers, or to make power traces broader than signal traces.
In integrated circuits, small capacitors can be formed through appropriate patterns of metallization on an isolating substrate.
Vacuum: Expensive, housed in glass or ceramic body, typically rated for 5kV - 30kV. Typically used in high power RF transmitters because the dielectric has virtually no loss and is self-healing. May be fixed or adjustable.

Image File history File links A circuit symbol. ... Image File history File links A circuit symbol. ... Image File history File links A circuit symbol. ... Image File history File links A circuit symbol. ... Image File history File links A circuit symbol. ... Image File history File links A circuit symbol. ... A crystal oscillator (sometimes abbreviated to XTAL on schematic diagrams) is an electronic circuit that uses the mechanical resonance of a physical crystal of piezoelectric material along with an amplifier and feedback to create an electrical signal with a very precise frequency. ... The EIA Class 1 dielectric materials are ceramic dielectric materials used in ceramic capacitors of small values (typ. ... This page meets Wikipedias criteria for speedy deletion. ... The EIA Class 2 dielectric materials are ceramic dielectric materials used in ceramic capacitors. ... Microphonics are noises in a loudspeaker caused by mechanical shock or vibration of the electronic components. ... The EIA Class 2 dielectric materials are ceramic dielectric materials used in ceramic capacitors. ... The EIA Class 2 dielectric materials are ceramic dielectric materials used in ceramic capacitors. ... Microphonics are noises in a loudspeaker caused by mechanical shock or vibration of the electronic components. ... Lead zirconium titanate (PZT, also Lead zirconate titanate) is a ceramic perovskite material that shows a marked piezoelectric effect - that is, it develops a voltage difference across two of its faces when compressed, and ferroelectric effect. ... In physics, the ferroelectric effect is an electrical phenomenon whereby certain ionic crystals may exhibit a spontaneous dipole moment. ... Polycarbonates are a particular group of thermoplastics. ... SEM picture of a bend in a high surface area polyester fiber with a seven-lobed cross section Polyester is a category of polymers, or, more specifically condensation polymers, which contain the ester functional group in their main chain. ... Biaxially-oriented polyethylene terephthalate (boPET) polyester film is used for its high tensile strength, chemical and dimensional stability, transparency, gas and aroma barrier properties and electrical insulation. ... For other uses, see Polystyrene (disambiguation). ... Polypropylene lid of a Tic Tacs box, with a living hinge and the resin identification code under its flap Polypropylene or polypropene (PP) is a thermoplastic polymer, used in a wide variety of applications, including food packaging, textiles, laboratory equipment, loudspeakers, automotive components, and polymer banknotes. ... Teflon is the brand name of a polymer compound discovered by Roy J. Plunkett (1910-1994) of DuPont in 1938 and introduced as a commercial product in 1946. ... Teflon is polytetrafluoroethylene (PTFE), a polymer of fluorinated ethylene. ... General Name, Symbol, Number silver, Ag, 47 Chemical series transition metals Group, Period, Block 11, 5, d Appearance lustrous white metal Atomic mass 107. ... rock with mica Mica sheet mica flakes The mica group of minerals includes several closely related materials having highly perfect basal cleavage. ... Electrolytic capacitors An electrolytic capacitor is a type of capacitor with a larger capacitance per unit volume than other types, making them valuable in relatively high-current and low-frequency electrical circuits. ... An electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, and switches. ... Various types of capacitors A capacitor (occasionally referred to using the older term condenser) is a device that stores energy in the electric field created between a pair of conductors on which equal but opposite electric charges have been placed. ... Close-up photo of one side of a motherboard PCB, showing conductive traces, vias and solder points for through-hole components on the opposite side. ... An integrated circuit (IC) is a thin chip consisting of at least two interconnected semiconductor devices, mainly transistors, as well as passive components like resistors. ... Look up Vacuum in Wiktionary, the free dictionary. ... RF may be: RF is the IATA code for Florida West International Airways Rf or RF may stand for: Radio frequency, a term in broadcasting. ...

Fixed capacitor comparisons

Capacitor type	Dielectric used	Advantages/applications	Disadvantages
Paper Capacitors	Paper or oil-impregnated paper	Impregnated paper was extensively used for older capacitors, using wax, oil, or epoxy as an impregnant. Oil-Kraft paper capacitors are still used in certain high voltage applications. Has mostly been replaced by plastic film capacitors.	Large size. Also, paper is highly hygroscopic, absorbing moisture from the atmosphere despite plastic enclosures and impregnants. Absorbed moisture degrades performance by increasing dielectric losses (power factor) and decreasing insulation resistance.
Metalized Paper Capacitors	Paper	Comparatively smaller in size than paper-foil capacitors	Suitable only for lower current applications. Has been largely superseded by metalized film capacitors
PET film or Mylar film Capacitor	Polyester film	Smaller in size when compared to paper or polypropylene capacitors of comparable specifications. May use plates of foil, metalized film, or a combination. Mylar capacitors have almost completely replaced paper capacitors for most DC electronic applications. Operating voltages up to 60,000VDC and operating temperatures up to 125ºC. Low moisture absorption.	Temperature stability is poorer than paper capacitors. Useable at low (AC power) frequencies, but inappropriate for RF applications due to excessive dielectric heating.
Kapton Capacitor	Kapton polyimide film	Similar to PET film, but significantly higher operating temperature (up to 250ºC).	Higher cost than PET. Temperature stability is poorer than paper capacitors. Useable at low (AC power) frequencies, but inappropriate for RF applications due to excessive dielectric heating.
Polystyrene Capacitor	Polystyrene	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	Maximum operating temperature is limited to about +85ºC. Comparatively bigger in size.
Polycarbonate Plastic Film Capacitor	Polycarbonate	Superior insulation resistance, dissipation factor, and dielectric absorption versus polystyrene capacitors. Moisture pick-up is less, with about +/- 80 ppm temperature co-efficient. Can use full operating voltage across entire temperature range (-55ºC to 125ºC)	Maximum operating temperature limited to about 125ºC.
Polypropelene Plastic Film Capacitors	Polypropylene	Has become the most popular capacitor dielectric. Extremely low dissipation factor, higher dielectric strength than polycarbonate and polyester films, low moisture absorption, and high insulation resistance. May use plates of foil, metalized film, or a combination. Film is compatible with self-healing technology to improve reliability. Usable in high frequency applications due to very low dielectric losses. Larger value and higher voltage types from 1 to 100μF at up to 440V AC are used as run capacitors in some types of single phase electric motors.	More susceptible to damage from transient overvoltages or voltage reversals than oil-impregnated Kraft paper for pulsed power energy discharge applications.
Polysulphone Plastic Film Capacitors	Polysulfone	Similar to polycarbonate. Can withstand full voltage at comparatively higher temperatures. Moisture pick-up is typically 0.2%, limiting its stability.	Very limited availability and higher cost
PTFE Fluorocarbon (TEFLON) Film Capacitors	Polytetrafluoroethylene	Lowest loss solid dielectric. Operating temperatures up to 250ºC, extremely high insulation resistance, and good stability. Used in stringent, mission-critical applications	Large size (due to low dielectric constant), and higher cost than other film capacitors.
Polyamide Plastic Film Capacitors	Polyamide	Operating temperatures of up to 200ºC. High insulation resistance, good stability and low dissipation factor.	Large size and high cost.
Metalized Plastic Film Capacitors	Polyester or Polycarbonate	Reliable and significantly smaller in size. Thin metalization can be used to advantage by making capacitors "self healing".	Thin plates limit maximum current carrying capability.
Stacked Plate Mica Capacitors	Mica	Advantages of mica capacitors arise from the fact that the dielectric material (mica) is inert. It does not change physically or chemically with age and it has good temperature stability. Very resistant to corona damage	Unless properly sealed, susceptible to moisture pick-up which will increase the power factor and decrease insulation resistance. Higher cost due to scarcity of high grade dielectric material and manually-intensive assembly.
Metalized Mica or Silver Mica Capacitors	Mica	Have the above mentioned advantages. In addition, they have much reduced moisture infiltration.	Higher cost
Glass Capacitors	Glass	Similar to Mica Capacitors. Stability and frequency characteristics are better than mica capacitors. Ultra-reliable, ultra-stable, and resistant to nuclear radiation.	High cost.
Class-I Temperature Compensating Type Ceramic Capacitors	Mixture of complex Titanate compounds	Low cost and small size, excellent high frequency characteristics and good reliability. Predictable linear capacitance change with operating temperature. Available in voltages up to 15,000 volts	Capacitance changes with change in applied voltage, with frequency and with aging effects.
Class-II High dielectric strength Type Ceramic Capacitors	Barium titanate based dielectrics	Smaller than Class-I type due to higher dielectric strength of ceramics used. Available in voltages up to 50,000 volts.	Not as stable as Class-I type with respect to temperature, and capacitance changes significantly with applied voltage.
Aluminium Electrolytic Capacitors	Aluminium oxide	Very large capacitance to volume ratio, inexpensive, polarized. Primary applications are as smoothing and reservoir capacitors in power supplies.	Dielectric leakage is high, large internal resistance and inductance limits high frequency performance, poor low temperature stability and loose tolerances. May vent or burst open when overloaded and/or overheated. Limited to about 500 volts.
Tantalum Electrolytic Capacitors	Tantalum oxide	Large capacitance to volume ratio, smaller size, good stability, wide operating temperature range, long reliable operating life. Extensively used in miniaturised equipment and computers. Available in both polarised and unpolarised varieties. Solid tantalum capacitors have much better characteristics than their wet counterparts.	Higher cost than aluminum electrolytic capacitors. Voltage limited to about 50 volts. Explodes quite violently when voltage rating, current rating, or slew rates are exceeded, or when a polarized version is subjected to reverse voltage.
Electrolytic double-layer capacitors (EDLC) Supercapacitors	Thin Electrolyte layer and Activated Carbon	Extremely large capacitance to volume ratio, small size, low ESR. Available in hundreds, or thousands, of farads. A relatively new capacitor technology. Often used to temporarily provide power to equipment during battery replacement. Can rapidly absorb and deliver larger currents than batteries during charging and discharging, making them valuable for hybrid vehicles. Polarized, low operating voltage (volts per capacitor cell). Groups of cells are stacked to provide higher overall operating voltage.	Relatively high cost.
Alternating current oil-filled Capacitors	Oil-impregnated paper	Usually PET or polypropylene film dielectric. Primarily designed to provide very large capacitance for industrial AC applications to withstand large currents and high peak voltages at power line frequencies. The applications include AC motor starting and running, phase splitting, power factor correction, voltage regulation, control equipment, etc..	Limited to low frequency applications due to high dielectric losses at higher frequencies.
Direct current oil-filled capacitors	Paper or Paper-polyester film combination	Primarily designed for DC applications such as filtering, bypassing, coupling, arc suppression, voltage doubling, etc...	Operating voltage rating must be derated as per the curve supplied by the manufacturer if the DC contains ripple. Physically larger than polymer dielectric counterparts.
Energy Storage Capacitors	Kraft capacitor paper impregnated with electrical grade castor oil or similar high dielectric constant fluid, with extended foil plates	Designed specifically for intermittent duty, high current discharge applications. More tolerant of voltage reversal than many polymer dielectrics. Typical applications include pulsed power, electromagnetic forming, pulsed lasers, Marx generators, and pulsed welders.	Physically large and heavy. Significantly lower energy density than polymer dielectric systems. Not self-healing. Device may fail catastrophically due to high stored energy.
Vacuum Capacitors	Vacuum capacitors use highly evacuated glass or ceramic chamber with concentric cylindrical electrodes.	Extremely low loss. Used for high voltage high power RF applications, such as transmitters and induction heating where even a small amount of dielectric loss would cause excesive heating. Can be self-healing if arc-over current is limited.	Very high cost, fragile, physically large, and relatively low capacitance.

A dielectric, or electrical insulator, is a substance that is highly resistant to the flow of electric current and has a relative permittivity greater than unity. ... Piece of paper Paper is a thin, flat material produced by the compression of fibers. ... Natural olive oil Synthetic motor oil Oil, in a general sense, is a chemical compound that is not miscible with water, and is in a liquid state at ambient temperatures. ... In electrical engineering High voltage refers to a voltage which is high. ... Plastic covers a range of synthetic or semisynthetic polymerization products. ... A hygroscopic substance is a substance that absorbs water readily from its surroundings. ... Moisture generally refers to the presence of water in trace amounts. ... Layers of Atmosphere (NOAA) Air redirects here. ... Plastic covers a range of synthetic or semisynthetic polymerization products. ... The power factor of an AC electric power system is defined as the ratio of the real power to the apparent power. ... This article or section is in need of attention from an expert on the subject. ... Hot metal work from a blacksmith Look up Metal in Wiktionary, the free dictionary. ... Biaxially-oriented polyethylene terephthalate (boPET) polyester film is used for its high tensile strength, chemical and dimensional stability, transparency, gas and aroma barrier properties and electrical insulation. ... Direct current (DC or continuous current) is the continuous flow of electricity through a conductor such as a wire from high to low potential. ... Look up AC, ac in Wiktionary, the free dictionary. ... RF may be: RF is the IATA code for Florida West International Airways Rf or RF may stand for: Radio frequency, a term in broadcasting. ... Kapton is a polyimide film developed by DuPont which can remain stable in a wide range of temperatures, from -269°C to 400°C. Kapton is used in, among other things, flexible printed circuits and spacesuits. ... Polyimide is a polymer of imide monomers. ... Look up AC, ac in Wiktionary, the free dictionary. ... RF may be: RF is the IATA code for Florida West International Airways Rf or RF may stand for: Radio frequency, a term in broadcasting. ... For other uses, see Polystyrene (disambiguation). ... The temperature coefficient is the relative change of a physical property when the temperature is changed by 1 K (kelvin). ... Polycarbonates are a particular group of thermoplastics. ... This article or section is in need of attention from an expert on the subject. ... Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ... A wave that loses amplitude is said to dissipate. ... Polypropylene lid of a Tic Tacs box, with a living hinge and the resin identification code under its flap Polypropylene or polypropene (PP) is a thermoplastic polymer, used in a wide variety of applications, including food packaging, textiles, laboratory equipment, loudspeakers, automotive components, and polymer banknotes. ... Pulsed power is the science and technology of accumulating energy over a relatively long period of time and releasing it very quickly. ... Polysulfone, or PSU, is a polymer thermoplastic material. ... Teflon is polytetrafluoroethylene (PTFE), a polymer of fluorinated ethylene. ... Teflon is polytetrafluoroethylene (PTFE), a polymer of fluorinated ethylene. ... A polyamide is a polymer containing monomers joined by peptide bonds. ... SEM picture of a bend in a high surface area polyester fiber with a seven-lobed cross section Polyester is a category of polymers, or, more specifically condensation polymers, which contain the ester functional group in their main chain. ... Polycarbonates are a particular group of thermoplastics. ... In electricity, current refers to electric current, which is the flow of electric charge. ... rock with mica Mica sheet mica flakes The mica group of minerals includes several closely related materials having highly perfect basal cleavage. ... In English, to be inert is to be in a state of doing little or nothing. ... Since antiquity, people have tried to understand the behavior of matter: why unsupported objects drop to the ground, why different materials have different properties, and so forth. ... Chemistry (in Greek: χημεία) is the science of matter and its interactions with energy and itself (see physics, biology). ... In electricity, a corona discharge is an electrical discharge brought on by the ionization of a fluid surrounding a conductor, which occurs when the potential gradient exceeds a certain value, in situations where sparking (also known as arcing) is not favoured. ... See: espionage, urban exploration, entryism, heating, ventilation, and air conditioning. ... Glass can be made transparent and flat, or into other shapes and colours as shown in this ball from the Verrerie of Brehat in Brittany. ... The chemical compound Titanic acid, Ti(OH)4, is a white weak acid that is a hydrated form of titanium dioxide. ... A chemical compound is a chemical substance formed from two or more elements, with a fixed ratio determining the composition. ... Sine waves of various frequencies; the lower waves have higher frequencies than those above. ... The word linear comes from the Latin word linearis, which means created by lines. ... // Definition Capacitance is a measure of the amount of electric charge stored (or separated) for a given electric potential. ... Barium titanate is an oxide of barium and titanium with the chemical formula BaTiO3. ... An electrolyte is a substance which dissociates free ions when dissolved (or molten), to produce an electrically conductive medium. ... Flash point Non-flammable. ... Wiktionary has related dictionary definitions, such as: resistance Resistance may refer to: Antibiotic resistance, the ability of a microorganism to withstand the effects of an antibiotic Disease resistance, in immunology; see also disease resistance in fruit and vegetables Resistance, in physics, a force that tends to oppose motion Friction, the... Inductance (or electric inductance) is a measure of the amount of magnetic flux produced for a given electric current. ... The cross of the war memorial and a menorah for Hanukkah coexist in Oxford. ... An electrical overload is a situation where an electrical machine or system is subjected to a greater load than it was designed for. ... Tantalum pentoxide is Ta2O5, also known as tantalum(V) oxide. ... This article treats polarization in electrodynamics. ... In jewelry, a solid gold piece is the alternative to gold-filled or gold-plated jewelry. ... Wet could refer to: The condition of being liquid. ... A supercapacitor or an ultracapacitor is an electrochemical capacitor that has an unusually large amount of energy storage capability relative to its size when compared to common capacitors. ... An electrolyte is a substance that dissociates into free ions when dissolved (or molten), to produce an electrically conductive medium. ... Activated carbon (also called activated charcoal) is the more general term which includes carbon material mostly derived from charcoal. ... 2004 Toyota Prius, a hybrid gas-electric vehicle Honda Insight, the first hybrid gas-electric vehicle sold in North America 2006 Honda Civic Hybrid A hybrid vehicle is a vehicle using an on-board Rechargeable energy storage system (RESS) and a fueled propulsion power source for vehicle propulsion. ... Natural olive oil Synthetic motor oil Oil, in a general sense, is a chemical compound that is not miscible with water, and is in a liquid state at ambient temperatures. ... Look up AC, ac in Wiktionary, the free dictionary. ... Power Line is a neoconservative blog run by three lawyers: John H. Hinderaker (Hindrocket), Scott W. Johnson (The Big Trunk) and Paul Mirengoff (Deacon). Power Line covers political and social issues from a conservative viewpoint. ... A motor is a device that converts energy into mechanical power, and is often synonymous with engine. ... Phase is an overloaded word used for: instantaneous phase: the current position in the cycle of something that changes cyclically phase shift: a constant difference/offset between two instantaneous phases, particularly when one is a standard reference Waves are amplitudes that change cyclically, often modeled as sinusoidal functions of time... The power factor of an AC electric power system is defined as the ratio of the real power to the apparent power. ... Television signal splitter consisting of a hi-pass and a lo-pass filter. ... In telecommunications, the term bypass has these meanings: 1. ... In electronics and telecommunication, coupling is the desirable or undesirable transfer of energy from one medium, such as a metallic wire or an optical fiber, to another medium, including fortuitous transfer. ... An electric arc can melt calcium oxide. ... The Kraft process is used in production of paper pulp and involves the use of caustic sodium hydroxide and sodium sulfide to extract the lignin from the wood fiber in large vats called digesters. ... The article on electrical energy is located elsewhere. ... Castor oil is a vegetable oil obtained from the castor bean (or preferably castor seed as the castor plant (Ricinus communis) is not a member of the bean family). ... Pulsed power is the science and technology of accumulating energy over a relatively long period of time and releasing it very quickly. ... Electromagnetic forming (EM forming) is a high energy rate metal forming process, that uses ultrastrong pulsed magnetic fields, to reshape metal parts rapidly . ... Lasers range in size from microscopic diode lasers (top) with numerous applications, to football field sized neodymium glass lasers (bottom) used for inertial confinement fusion, nuclear weapons research and other high energy density physics experiments. ... A Marx generator is a type of electrical circuit first described by Erwin Marx in 1924 whose purpose is to generate a high voltage pulse. ... Welding is a fabrication process that joins materials, usually metals or thermoplastics, by causing coalescence. ... Look up Vacuum in Wiktionary, the free dictionary. ... In electrical engineering High voltage refers to a voltage which is high. ... RF may be: RF is the IATA code for Florida West International Airways Rf or RF may stand for: Radio frequency, a term in broadcasting. ... An electric arc can melt calcium oxide. ...

Variable capacitors

Main article: Variable capacitor

Variable capacitors may have their capacitance intentionally and repeatedly changed over the life of the device. They include capacitors that use a mechanical construction to change the distance between the plates, or the amount of plate surface area which overlaps, and variable capacitance diodes that change their capacitance as a function of the applied reverse bias voltage. A variable capacitor is a capacitor whose capacitance may be intentionally and repeatedly changed mechanically or electronically. ... A varicap diode, varactor diode or tuning diode is a type of diode used in electronic circuits. ...

Variable capacitance is also used in sensors for physical quantities, including microphones, pressure and hygro sensors.

Non-ideal properties of practical capacitors

Q factor, dissipation and tan-delta

Capacitors have "Q" (quality) factor (and the inverse, dissipation factor or tan-delta) which relates capacitance at a certain frequency to the dissipation factor (dielectric loss). The higher this figure, the lossier the capacitor. Tan-delta is the tangent of the phase angle between voltage and current in the capacitor. This angle is sometimes called the loss angle. It is related to the power factor which is zero for an ideal capacitor. The dissipation factor is a measure of the loss of power which takes place in virtually all dielectric materials, usually in the form of heat. ...

Equivalent series resistance (ESR)

This is an effective resistance that is used to describe the resistive parts of the impedance of certain electronic components. The theoretical treatment of devices such as capacitors and inductors tends to assume they are ideal or "perfect" devices, contributing only capacitance or inductance to the circuit. However, all physical devices are constructed of materials with finite electrical resistance, which means that all real-world components contain some resistance in addition to their other properties. A low ESR capacitor typically has an ESR of 0.01 Ω. Low values are preferred for high-current, pulse applications. Low ESR capacitors have the capability to deliver huge currents into short circuits, which can be dangerous. Equivalent series resistance (ESR) is a theoretical device designed to accommodate the real-world limitations of electronic components. ...

For capacitors, ESR takes into account the internal lead and plate resistances and other factors. An easy way to deal with these inherent resistances in circuit analysis is to express each real capacitor as a combination of an ideal component and a small resistor in series, the resistor having a value equal to the resistance of the physical device.

Equivalent series inductance (ESL)

ESL in signal capacitors is mainly caused by the leads used to connect the plates to the outside world and the series interconnects used to join sets of plates together internally. For any real-world capacitor, there is a frequency above DC at which it ceases to behave as a pure capacitance. This is called the (first) resonant frequency. This is critically important with decoupling high-speed logic circuits from the power supply. The decoupling capacitor supplies transient current to the chip. Without decouplers, the IC demands current faster than the connection to the power supply can supply it, as parts of the circuit rapidly switch on and off. Large capacitors tend to have much higher ESL than small ones. As a result, electronics will frequently use multiple bypass capacitors — a small 0.1 µF rated for high frequencies and a large electrolytic rated for lower frequencies, and occasionally, an intermediate value capacitor. In Electronics, the Equivalent Series Inductance (ESL, the L is the symbol for inductors) describes the parasitic inductance found in real capacitors (symbol C), modeled as a inductance in series to an ideal capacitor. ... In physics, decoupling is the general phenomenon in which the interactions between some physical objects (such as elementary particles) disappear. ... Transient means passing with time. ...

Maximum Voltage and Current

Important properties of capacitors are the maximum working voltage (potential, measured in volts) and the amount of energy lost in the dielectric. For high-power or high-speed capacitors, the maximum ripple current, peak current, fault current, and percent voltage reversal are further considerations.

Temperature dependence

Another major non-ideality is temperature coefficient (change in capacitance with temperature) which is usually quoted in parts per million (ppm) per degree Celsius.

Aging

When refurbishing old (especially audio) equipment, it is a good idea to replace all of the electrolyte-based caps. After long storage, the electrolyte and dielectric layer within electrolytic capacitors may deteriorate; before powering up equipment with old electrolytics, it may be useful to apply low voltage to allow the capacitors to reform before applying full voltage. Non polarised capacitors also suffer from aging, changing their values slightly over long periods of time.

Dielectric absorption (soakage)

In the construction of long-time-constant integrators, it is important that the capacitor will not retain a residual charge when shorted. This phenomenon of unwanted charge storage is called dielectric absorption or soakage, and it effectively creates a memory effect in the capacitor. This is a non-linear phenomenon, and is also important when building very low distortion filters. This is also why, for safety, high voltage capacitors are stored with their terminals short circuited.

Non-linearity

Capacitors may also change capacitance with applied voltage. This effect is more prevalent in high 'k' ceramic and some high voltage capacitors. This can be another small source of non-linearity when building low distortion filters.

Leakage

Capacitors also have some level of parasitic resistance across the terminals which is called 'leakage'. This fundamentally limits how long capacitors can store charge. Historically, this was a major source of problems in some types of applications (long RC timers, sample-and-holds, etc.)

Component values and identification

Standard values

In the early days of electronics, components were often made to fit a specific need, the values of early capacitors were of arbitrary (usually integer) base numbers. The more common values included 1.0, 1.5, 2.0, 3.0, 5.0, 6.0, and 8.0 as base numbers, but they were not necessarily limited to these values. Values were generally in microfarads (µF) and could be multiplied by any power of ten; picofarads were often called micro-microfarads (µµF) then.

In the late 1960s, a standardized set of geometrically increasing base values was introduced. According to the number of values per decade, these were called the E3, E6 or E12 series:

Series	Values
E3	1.0				2.2				4.7
E6	1.0		1.5		2.2		3.3		4.7		6.8
E12	1.0	1.2	1.5	1.8	2.2	2.7	3.3	3.9	4.7	5.6	6.8	8.2

The same series are used for resistors, where E24/E48/E96 series are additionally used for even lower-tolerance components. These number series are known as preferred values. In industrial design, product developers must choose numerous lengths, distances, diameters, volumes, and other characteristic quantities. ...

Since most electrolytic capacitors have a tolerance range of ±20%, meaning that the manufacturer guarantees that the actual value of the capacitor lies within ±20% of its nominal value, they are normally available in E6 (or even just E3) series values only (e.g. 2200 µF, 3300 µF, 4700 µF) – the tolerance ranges overlap the intermediate values from the next higher series anyway.

Other types of capacitors, e.g. ceramic, can be manufactured to tighter tolerances and are available in E12 values (e.g. 47 pF, 56 pF, 68 pF).

Capacitors were once specified by their values in either microfarads or picofarads, which meant that both very small (such as 0.01 µF) and very large (such as 10,000 pF) numbers were in common use. Nowadays, it is considered preferable to use the nanofarad as well, and specify all values in the numeric range 1 - 999 only; this makes the examples given above equal to 10 nF (yes, they are both the same!). Above 999 µF, the practice is not yet in common use; capacitors are not usually specified in millifarads (mF), probably because it would be too easily confused with microfarads (for which mF was once an acceptable abbreviation).

A table giving translations of previous commonly used multiples is as follows:

preferred	in pF	in nF	in µF
1pF	1	0.001	0.000,001
10pF	10	0.01	0.000,01
100pF	100	0.1	0.000,1
1nF	1000	1	0.001
10nF	10,000	10	0.01
100nF	100,000	100	0.1
1µF	1,000,000	1000	1

Colour coding

Colour	Significant digits	Multiplier	Capacitance tolerance	Characteristic	DC working voltage	Operating temperature	EIA/vibration
Black	0	1	±20%	—	—	−55 °C to +70 °C	10 to 55 Hz
Brown	1	10	±1%	B	100	—	—
Red	2	100	±2%	C	—	−55 °C to +85°C	—
Orange	3	1,000	—	D	300	—	—
Yellow	4	10,000	—	E	—	−55 °C to +125°C	10 to 2000 Hz
Green	5	—	±5%	F	500	—	—
Blue	6	—	—	—	—	−55 °C to +150°C	—
Violet	7	—	—	—	—	—	—
Grey	8	—	—	—	—	—	—
White	9	—	—	—	—	—	EIA
Gold	—	—	±0.5%*	—	1000	—	—
Silver	—	—	±10%	—	—	—	—

*Or ±0.5 pF, whichever is greater. EIA may refer to the following: Electronic Industries Alliance Energy Information Administration Environmental Impact Assessment Enzyme-Linked Immunosorbent Assay Equity Indexed Annuity Exercise-induced anaphylaxis This is a disambiguation page, a list of pages that otherwise might share the same title. ...

References

Glenn Zorpette Super Charged: A Tiny South Korean Company is Out to Make Capacitors Powerful enough to Propel the Next Generation of Hybrid-Electric Cars, IEEE Spectrum, January, 2005 Vol 42, No. 1, North American Edition.
The ARRL Handbook for Radio Amateurs, 68th ed, The Amateur Radio Relay League, Newington CT USA, 1991
Basic Circuit Theory with Digital Computations, Lawrence P. Huelsman, Prentice-Hall, 1972
Philosophical Transactions of the Royal Society LXXII, Appendix 8, 1782 (Volta coins the word condenser)
A. K. Maini Electronic Projects for Beginners, "Pustak Mahal", 2nd Edition: March, 1998 (INDIA)
Spark Museum (von Kleist and Musschenbroek)
Biography of von Kleist

Category: Capacitors IEEE Spectrum is a magazine edited by the Institute of Electrical and Electronics Engineers. ...

COMMENTARY

Share your thoughts, questions and commentary here

Want to know more?
Search encyclopedia, statistics and forums:

Feeds | Contact
The Wikipedia article included on this page is licensed under the GFDL.
Images may be subject to relevant owners' copyright.
All other elements are (c) copyright NationMaster.com 2003-5. All Rights Reserved.
Usage implies agreement with terms.

Contents

Capacitor construction GA_googleFillSlot("encyclopedia_square");