Integrated CircuitsAn integrated circuit contains transistors, capacitors, resistors and other parts packed in high density on one chip.Although the function is similar to a circuit made with separate components, the internal structure of the components are different in an integrated circuit.The transistors, resistors, and capacitors are formed very small, and in high density on a foundation of silicon. They are formed by a variation of printing technology.There are many kind of ICs, including special use ICs.

The top left device in the photograph is an SN7400. It contains 4 separate "2 input NAND" circuits. There are 7 pins on each side, 14 pins total.ICs in this form are called Dual In line Package (DIP).When an IC has only one row of pins, it os called a Single In line Package (SIP).The number of pins changes depending on the function of IC.

At the bottom left is an IC socket for use with 14 pin DIP ICs.ICs can be attached directly to the printed circuit board with solder, but it's better to use an IC socket, because you can easily

exchange it should the IC fail.

On the top right is an LM386N audio amplifier. It can be used for amplification of low frequency, low power signals. IT has 8 pins and the maximum output is 660mW.

On the bottom right is a TA7368P, which also is for amplification of low frequency electric power. It has a maximum output of 1.1 watts.It is a 9 pin SIP IC.

Common ICs

Below, the most common ICs are shown. (Those parts that I use most.)For extensive details on each part, see the corresponding data sheet.The part numbers of the SN74 series ICs are written with a 74, often followed by LS or HC.LS (Low power Shottky) indicates low power consumption. HC indicates the device is High speed C-MOS (Complementary-Metal Oxide Semiconductor), and is also a low power consumption IC.The average current consumption for each type of chip is listed below.The current shown is for when the device is in a LOW state output. In the case of the LOW state output, current consumption is much greater than in the HIGH state output.SN7400 ----- 22mA

SN74LS00 ----- 4.4mA

SN74HC00 ----- 0.02mA

Several kinds of ICs are not available in the LS or HC type. For example, SN7445 is not available in LS or HC. It is available only as SN7445, the normal type.

Name Function Vcc Pin Assign(Top View) RemarksSN74HC00 Quad 2 Input

NAND+5V 2 input NAND circuits entered

4 pieces

SN74HC04 Hex Inverters +5V Inverter circuit entered 6 piecesDetails

SN74LS42 BCD to DECIMALDecoder

+5V One of output takes LOW state serected by the binary input.

SN7445 O.C. BDC to DECIMALDecoder/Driver

+5V Open collector type of 7442

Max current of output is 80mA.

SN74LS47 BCD to SegmentDecoder/Driver

+5V

Front ViewDriving IC of ‚Vsegments LED.Open collector typeMax resistance voltage:15V6 and 9 disply type:Related 74247

SN74HC73 Dual JK-FFsWith Clear

+5V 2 pieces of JK-FF

SN74LS90 Decade Counter +5V Asynchronous 2 + 5 counter.Async preset : 9Async clearRelated7429074390

SN74HC93 4-Bit BinaryCounter

+5V Asynchronous 2 + 8 counter.

SN74HC123 Dual RetriggaerableSingle Shot

+5V Single shot resister holds the output in the required time from the input states goes to ON.The output holding time corresponds to C(capacitor) and R(resistor) connected to the Cext(External capacitor) and Rext(External resistor) respectivly.

SN74LS247 BCD to SegmentDecoder/Driver

+5V

Front View

6 and 9 disply type:Related 7447

SN74LS290 Decade Counter +5V This type is the same as the SN7490, with a different layout of pins.Related749074390

SN74HC390 Dual DecadeCounters

+5V Type that inserted 2 SN7490.Presetting 9 is omitted .Related749074290

4040B 12Bit BinaryCounter(CMOS)

+5V 12-stage Binary counter.It has a clear function.Counts downward with an external clock pulse.

4541B ProgarammableOscillator/Timer(CMOS)

+5V Programmable 16 stage binary counter.Used in RC oscillation circuits, power reset, output control circuits.Tap outputs of 8, 10, 13, 16 bits are possible by the control terminal.

NE555 Timer +4.5 to +16V

Max frequency: 500kHzTemperature drift: 0.005%/°C.Max output current: 200mA.Delay time setting:several micro sec to several hours

LM386N-1 Low frequency electric power amplifier

+4 to 12V

Max output: 660mWLoad: 8 to 32-ohmWaiting current: 4mA

LM386N-4 Low frequency electric power amplifier

+5 to 18V

Max output: 1.25WLoad: 8 to 32-ohmWaiting current: 4mA

TA7368P Low frequency electric power amplifier

+2 to +10V

Max output: 1.1WLoad: 4 to 16-ohm

uPC319 Voltage comparator 5 to 18V

±5to±18V

Standard general use comparator with single power supply/dual power supply operation

Other compatible ICsLM319NJM319AN1319

7975 Multi-melody IC(CMOS)

+1.5 to +3V

Melody IC that includes 8 pre-programmed melodies.It has 2 sound resources and a settable envelope.

TitleGreen-SleevesFur EliseHeavenly CreaturesIch bin ein musikanteValse FavoriteHolderiaAmaryllisHome On The Range

Three Terminal Voltage Regulator

It is very easy to get stabilized voltage for ICs by using a three terminal voltage regulator.The power supply voltage for a car is +12V - +14V. At this voltage, some ICs can not operate directly except for the car component ICs. In this case, a three terminal voltage regulator is necessary to get the required voltage.The three terminal voltage regulator outputs stabilized voltage at a lower level than the higher input voltage. A voltage regulator cannot put out higher voltage than the input voltage. They are similar in appearance to a

transistor.

On the left in the photograph is a 78L05. The size and form is similar to a 2SC1815 transistor.The output voltage is +5V, and the maximum output current is about 100mA.The maximum input voltage is +35V. (Differs by manufacturer.)

On the right is a 7805. The output voltage is +5V, and maximum output current is 500mA to 1A. (It depends on the heat sink used)The maximum input voltage is also +35V.

There are many types with different output voltages.5V, 6V, 7V, 8V, 9V, 10V, 12V, 15V, 18V

Component Lead of Three Terminal Voltage RegulatorBecause the component leads differ between kinds of regulators,

you need to confirm the leads with a datasheet, etc.

Example of 78L05Part number is printed on the flat face of the regulator, and indicates the front.

Right side : InputCenter : GroundLeft side : Output

Example of 7805Part number is printed on the flat face of the regulator, and indicates the front.

Right side : OutputCenter : GroundLeft side : Input

Opposite from 78L05.

Types of capacitorFrom Wikipedia, the free encyclopedia

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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).

Contents[hide]

1 Capacitor construction 2 Types of dielectric 3 Fixed capacitor comparisons

4 Variable capacitors 5 Non-ideal properties of practical capacitors

o 5.1 Breakdown voltage o 5.2 Q factor, dissipation and tan-delta o 5.3 Equivalent series resistance (ESR) o 5.4 Equivalent series inductance (ESL) o 5.5 Maximum voltage and current o 5.6 Temperature dependence o 5.7 Aging o 5.8 Dielectric absorption (soakage) o 5.9 Voltage non-linearities o 5.10 Leakage

6 Component values and identification o 6.1 Standard values o 6.2 Capacitor markings

6.2.1 Numerical markings 6.2.2 Colour coding

7 See also 8 Notes 9 References 10 External links

[edit] 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.

Many types of capacitors are available commercially, with capacitance ranging from the picofarad, microfarad 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.

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 electron emission. Air has a 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. High voltage capacitors need large, smooth, and round terminals to prevent corona discharge.

[edit] Types of dielectric

CapacitorPolarizedCapacito

r

VariableCapacitor

Capacitor symbols

Air-gap: air-gap capacitors have 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.

o C0G or NP0: typically 1 pF to 0.1 µF, 5%. High tolerance and good temperature performance. Larger and more expensive.

o X7R : typically 100 pF to 22 µF, 10%. Good for non-critical coupling, timing applications. Subject to microphonics. Temperature up to 125°C

o X8R : typically 100 pF to 10 µF, 25-100v, 5-10%. Good for high temperature up to 150°Co Z5U or 2E6: typically 1 nF to 10 µF, 20%. Good for bypass, coupling applications. Low

price and small size. Subject to microphonics.o Ceramic chip: 1% accurate, values up to about 1 µF, typically made from Lead zirconate

titanate (PZT) ferroelectric ceramic Gimmick: these capacitors are made by twisting together 2 pieces of insulated wire. Values

usually range from 3 pF to 15 pF. Usually used in homemade VHF circuits for oscillation feedback.

Trimmer: these capacitors have a rotating plate (which can be rotated to change the capacitance) separated from a fixed plate by a dielectric medium. Typically values range from 5 pF to 60 pF.

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 kV used for motor starting and high-voltage power supplies, and up to 25 kV for large oil-impregnated energy discharge types.

Polycarbonate : good for filters, low temperature coefficient, good aging, expensive. Polyester , (PET film): (from about 1 nF to 10 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. Silver 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 rechargeable 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 : vacuum variable capacitors are generally expensive, housed in a glass or ceramic body, typically rated for 5-30 kV. Typically used in high power RF transmitters because the dielectric has virtually no loss and is self-healing. May be fixed or adjustable.

[edit] Fixed capacitor comparisonsCapacitor type Dielectric used Features/applications Disadvantages

Paper CapacitorsPaper 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 impregnates. Absorbed moisture degrades performance by increasing dielectric losses (power factor) and decreasing insulation resistance.

Metalized Paper Capacitors

PaperComparatively smaller in size than paper-foil capacitors

Suitable only for lower current applications. Has been largely superseded by metalized film capacitors

PET 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. PET film capacitors have almost completely replaced paper capacitors for most DC electronic applications. Operating voltages up to 60,000 V DC and operating temperatures up to 125 °C. Low moisture absorption.

Temperature stability is poorer than paper capacitors. Usable at low (AC power) frequencies, but inappropriate for RF applications due to excessive dielectric heating.

Kapton CapacitorKapton polyimide film

Similar to PET film, but significantly higher operating temperature (up to 250 °C).

Higher cost than PET. Temperature stability is poorer than paper capacitors. Usable at low (AC power) frequencies, but inappropriate for RF applications due to excessive dielectric heating.

Polystyrene Polystyrene Excellent general purpose plastic film Maximum operating

Capacitor

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

temperature is limited to about +85 °C. 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 coefficient. Can use full operating voltage across entire temperature range (−55 °C to 125 °C)

Maximum operating temperature limited to about 125 °C.

Polypropylene Plastic Film Capacitors

Polypropylene

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 and high frequency high power applications such as induction heating (often combined with water-cooling) due to very low dielectric losses. Larger value and higher voltage types from 1 to 100 μF at up to 440 V AC are used as run capacitors in some types of single phase electric motors.

More susceptible to damage from transient over-voltages 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

Polytetra- fluoroeth ylene

Lowest loss solid dielectric. Operating temperatures up to 250 °C, 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

PolyamideOperating temperatures of up to 200 °C. 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

Silver mica capacitors 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 silver 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

Capacitance changes with change in applied voltage, with frequency and with aging effects.

to 15,000 volts

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.

Aluminum Electrolytic Capacitors

Aluminum 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.

Lithium Ion Capacitors

Lithium ion

The lithium ion capacitors have a higher power density as compared to batteries and LIC’s are safer in use than LIB’s in which thermal runaway reactions may occur. Compared to electric double layer capacitor (EDLC), the LIC has a higher output voltage. They both have similar power densities, but energy density of an LIC is much higher.

New technology.

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 miniaturized equipment and computers. Available in both polarized and unpolarized 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

Designed specifically for intermittent duty, high current discharge applications. More tolerant of voltage reversal than many polymer

Physically large and heavy. Significantly lower energy density than polymer dielectric systems. Not

high dielectric constant fluid, with extended foil plates

dielectrics. Typical applications include pulsed power, electromagnetic forming, pulsed lasers, Marx generators, and pulsed welders.

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 excessive heating. Can be self-healing if arc-over current is limited.

Very high cost, fragile, physically large, and relatively low capacitance.

A 12 pF, 20 kV fixed vacuum capacitor

Two 8 μF, 525 V paper electrolytic capacitors in a 1930s radio.[1]

Images of different types of capacitors

[edit] 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.

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

[edit] Non-ideal properties of practical capacitors

[edit] Breakdown voltage

Main article: Breakdown voltage

The breakdown voltage of the dielectric limits the power density of capacitors. For a particular dielectric, the breakdown voltage is proportional to the thickness of the dielectric.

If a manufacturer makes a new capacitor with the same dielectric as some old capacitor, but with half the thickness of the dielectric, the new capacitor has half the breakdown voltage of the old capacitor.

Because the plates are closer together, the manufacturer can put twice the parallel-plate area inside the new capacitor and still fit it in the same volume (capacitor size) as the old capacitor. Since the capacitance of a parallel-plate capacitor is given by:

this new capacitor has 4 times the capacitance as the old capacitor.

Since the energy stored in a capacitor is given by:

this new capacitor has the same maximum energy density as the old capacitor.

The energy density depends only on the dielectric. Making a few thick layers of dielectric (which can support a high voltage, but results in a low capacitance), or making many very thin layers of dielectric (which results in a low breakdown voltage, but a higher capacitance) has no effect on the energy density.

[edit] Q factor, dissipation and tan-delta

Capacitors have Q (quality) factor (and the inverse, dissipation factor, D or tan-delta) which relates capacitance at a certain frequency to the combined losses due to dielectric leakage and series internal resistance (also known as ESR) dissipation factor (dielectric loss). The lower the Q, the lossier the capacitor. Aluminum electrolytic types have typically low Q factors. High Q capacitors tend to exhibit low DC leakage currents. 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.

[edit] 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 (non-superconducting) 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.

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.

[edit] 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.

[edit] 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. Typically the voltage is 66% of the rated voltage. A voltage higher than that, usually reduces the life expectancy depending on manufacturer. The time for a voltage to discharge is 6 time constants.

[edit] 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.

[edit] Aging

When refurbishing old (especially audio) equipment, it is a good idea to replace all of the electrolyte-based capacitors. 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. Deteriorating capacitors are a frequent cause of hum in aging audio equipment.

Non-polarised capacitors also suffer from aging, changing their values slightly over long periods of time.

In high voltage DC applications, accumulated capacitor stress due to in-rush currents at circuit power-up can be minimized with a pre-charge circuit.

[edit] Dielectric absorption (soakage)

Some types of dielectrics, when they have been holding a voltage for a long time, maintain a "memory" of that voltage: after they have been quickly fully discharged and left without an applied voltage, a voltage will gradually be established which is some fraction of the original voltage. For some dielectrics 10% or more of the original voltage may reappear. This phenomenon of unwanted charge storage is called dielectric absorption or soakage, and it effectively creates a hysteresis or memory effect in capacitors.

The percentage of the original voltage restored depends upon the dielectric and is a non-linear function of original voltage.[2]

In many applications of capacitors dielectric absorption is not a problem but in some applications, such as long-time-constant integrators, sample-and-hold circuits, switched-capacitor analog-to-digital converters, and very low-distortion filters, it is important that the capacitor does not recover a residual charge after full discharge, and capacitors with low absorption are specified[3]. For safety, high-voltage capacitors are often stored with their terminals short circuited.

Some dielectrics have very low dielectric absorption, e.g., polystyrene, polypropylene, NPO ceramic, and Teflon. Others, in particular those used in electrolytic and supercapacitors, tend to have high absorption.

[edit] Voltage non-linearities

Capacitors may also change capacitance with applied voltage. This effect is more prevalent in high k ceramic and some high voltage capacitors. This is a small source of non-linearity in low-distortion filters and other analog applications.

[edit] Leakage

The resistance between the terminals of a capacitor is never truly infinite, leading to some level of d.c. 'leakage'; this ultimately limits how long capacitors can store charge. Before modern low-leakage dielectrics were developed this was a major source of problems in some applications (long time-constant timers, sample-and-holds, etc.).

[edit] Component values and identification

[edit] Standard values

Before 1960 electronic components values were not standardised. The more common, but not the only, values for capacitors were 1.0, 1.5, 2.0, 3.0, 5.0, 6.0, and 8.0 as base numbers multiplied by some negative or positive power of ten. Values of 0.001 µF and above were stated in microfarads (µF, or often mF); lower values were stated in micro-microfarads (µµF, now called picofarads, pF).

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

In many applications capacitors need not be specified to tight tolerance (they often need only to exceed a certain value); this is particularly true for electrolytic capacitors, which are often used for filtering and bypassing. Consequently capacitors, particularly electrolytics, often have a tolerance range of ±20% and need to be available only within E6 (or E3) series values.

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

With the introduction of S.I. submultiples of micro, nano, and pico, it became customary to specify capacitors with a number between 1 and 999 followed by farad, microfarad, nanofarad, or picofarad. While supercapacitors of up to 5,000 farads are produced, it is not usual to use kilofarad or millifarad.

[edit] Capacitor markings

Capacitors, like most other electronic components, have markings in their bodies to indicate their electrical characteristics, in particular capacitance, tolerance, working voltage and polarity (if relevant). For most types of capacitor, numerical markings are used, whereas some capacitors, especially older types, use colour coding.

[edit] Numerical markings

On capacitors that are large enough (e.g. electrolytic capacitors) the capacity and working voltage are printed on the body without encoding. Sometimes the markings also include the maximum working temperature, manufacturer's name and other information.

Smaller capacitors use a shorthand notation, to display all the relevant information in the limited space. The most commonly used format is: XYZ J/K/M VOLTS V, where XYZ represents the capacitance (calculated as XY×10Z pF), the letters J, K or M indicate the tolerance (±5%, ±10% and ±20% respectively) and VOLTS V represents the working voltage.

Polarised capacitors, for which one electrode must always be positive relative to the other, have clear polarity markings, usually a stripe or a "-" sign on the side of the negative electrode. Also, the negative lead is usually shorter.

Examples:

An electrolytic capacitor might be marked with the following information: 47µF 160V 105°C

A capacitor with the following text on its body: 105K 330V has a capacitance of 10×105 pF = 1 µF (±10%) with a working voltage of 330 V.

A capacitor with the following text: 473M 100V has a capacitance of 47×103 pF = 47 nF (±20%) with a working voltage of 100 V.

[edit] Colour coding

Main article: Electronic color code

Capacitors may be marked with 3 or more coloured bands or dots. 3-colour coding encodes most significant digit, second most significant digit, and multiplier. Additional bands have meanings which may vary from one type to another. Low-tolerance capacitors may begin with the first 3 (rather than 2) digits of the value. It is usually, but not always, possible to work out what scheme is used by the particular colours used. Cylindrical capacitors marked with bands may look like resistors.

Colour Significant digits

Multiplier Capacitance tolerance

Characteristic DC working

Operating temperature

EIA/vibration

voltage

Black 0 1 ±20% — —−55 °C to +70

°C10 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.

[edit] See also

The Wikibook Electronics has a page on the topic of

Capacitors

Capacitor plague (premature failure of certain incorrectly formulated electrolytic capacitors) Supercapacitor Electronic devices and circuits Electronic color code Inductor

[edit] Notes1. ̂ The abbreviation "MF" was used to indicate microfarads at the time; "MMF" was common for

micro-microfarad = 10-12 F or picofarads.2. ̂ "Modeling Dielectric Absorption in Capacitors" by Ken Kundert http://www.designers-

guide.org/Modeling/da.pdf3. ̂ "Understand Capacitor Soakage to Optimize Analog Systems" by Bob Pease 1982

http://www.national.com/rap/Application/0,1570,28,00.html

[edit] References Tre Clifford 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)

[edit] External links Spark Museum (von Kleist and Musschenbroek) Biography of von Kleist Modeling Dielectric Absorption in Capacitors A different view of all this capacitor stuff

Retrieved from "http://en.wikipedia.org/wiki/Types_of_capacitor"Categories: Capacitors

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Products Overview

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Safety Standard Recognized Ceramic Capacitors

Y Y1 & Y2 Ceramic Capacitors

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Items Type Image Voltage Dimension

Metal Oxide Varistors SSR 18V ~ 1100V 5D ~ 25D

CHAPTER 27 CAPACITORS AND DIELECTRICS.

o 27.1. Introduction o 27.2. The parallel-plate capacitor

Example: Problem 27.7 o 27.3. Capacitors in Combination

Example: Problem 27.10 o Example: Problem 27.13 o 27.4. Dielectrics

Example: Problem 27.19 o 27.5. Gauss Law in Dielectrics

Example: Problem 27.25 o 27.6 Energy in Capacitors

Example: Problem 27.40 Example: Problem 27.39

27. CAPACITORS AND DIELECTRICS.27.1. IntroductionA capacitor is an arrangement of conductors that is used to store electric charge. A very simple capacitor is an isolated metallic sphere. The potential of a sphere with radius R and charge Q is equal to

(27.1)

Equation (27.1) shows that the potential of the sphere is proportional to the charge Q on the conductor. This is true in general for any configuration of conductors. This relationship can be written as

(27.2)

where C is called the capacitance of the system of conductors. The unit of capacitance is the farad (F). The capacitance of the metallic sphere is equal to

(27.3)

27.2. The parallel-plate capacitorAnother example of a capacitor is a system consisting of two parallel metallic plates. In Chapter 26 it was shown that the potential difference between two plates of area A, separation distance d, and with charges +Q and -Q, is given by

(27.4)

Using the definition of the capacitance (eq.(27.2)), the capacitance of this system can be calculated:

(27.5)

Equation (27.2) shows that the charge on a capacitor is proportional to the capacitance C and to the potential V. To increase the amount of charge stored on a capacitor while keeping the potential (voltage) fixed, the capacitance of the capacitor will need to be increased. Since the capacitance of the parallel plate capacitor is proportional to the plate area A and inversely proportional to the distance d between the plates, this can be achieved by increasing the surface area A and/or decreasing the separation distance d. These large capacitors are usually made of two parallel sheets of aluminized foil, a few inches wide and several meters long. The sheets are placed very close together, but kept from touching by a thin sheet of plastic sandwiched between them. The entire sandwich is covered with another sheet of plastic and rolled up like a roll of toilet paper.

Example: Problem 27.7

The tube of a Geiger counter consists of a thin straight wire surrounded by a coaxial conducting shell. The diameter of the wire is 0.0025 cm and that of the shell is 2.5 cm. The length of the tube is 10 cm. What is the capacitance of a Geiger-counter tube ?

Figure 27.1. Schematic of a Geiger counter.

The problem will be solved under the assumption that the electric field generated is that of an infinitely long line of charge. A schematic side view of the tube is shown in Figure 27.1. The radius of the wire is rw, the radius of the cylinder is rc, the length of the counter is L, and the charge on the wire is +Q. The electric field in the region between the wire and the cylinder can be calculated using Gauss' law. The electric field in this region will have a radial direction and its magnitude will depend only on the radial distance r. Consider the cylinder with length L and radius r shown in Figure 27.1. The electric flux [Phi] through the surface of this cylinder is equal to

(27.6)

According to Gauss' law, the flux [Phi] is equal to the enclosed charge divided by [epsilon]0. Therefore

(27.7)

The electric field E(r) can be obtained using eq.(27.7):

(27.8)

The potential difference between the wire and the cylinder can be obtained by integrating the electric field E(r):

(27.9)

Using eq.(27.2) the capacitance of the Geiger tube can be calculated:

(27.10)

Substituting the values for rw, rc, and L into eq.(27.10) we obtain

(27.11)

27.3. Capacitors in CombinationThe symbol of a capacitor is shown in Figure 27.2. Capacitors can be connected together; they can be connected in series or in parallel. Figure 27.3 shows two capacitors, with capacitance C1 and C2, connected in parallel. The potential difference across both capacitors must be equal and therefore

(27.12)

Figure 27.2. Symbol of a Capacitor.

Figure 27.3. Two capacitors connected in parallel.

Using eq.(27.12) the total charge on both capacitors can be calculated

(27.13)

Equation (27.13) shows that the total charge on the capacitor system shown in Figure 27.3 is proportional to the potential difference across the system. The two capacitors in Figure 27.3 can be treated as one capacitor with a capacitance C where C is related to C1 and C2 in the following manner

(27.14)

Figure 27.4 shows two capacitors, with capacitance C1 and C2, connected in series. Suppose the potential difference across C1 is [Delta]V1 and the potential difference across C2 is [Delta]V2. A charge Q on the top plate will induce a charge -Q on the bottom plate of C1. Since electric charge is conserved, the charge on the top plate of C2 must be equal to Q. Thus the charge on the bottom plate of C2 is equal to -Q. The voltage difference across C1 is given by

(27.15)

and the voltage difference across C2 is equal to

(27.16)

Figure 27.4. Two capacitors connected in series.

The total voltage difference across the two capacitors is given by

(27.17)

Equation (27.17) again shows that the voltage across the two capacitors, connected in series, is proportional to the charge Q. The system acts like a single capacitor C whose capacitance can be obtained from the following formula

(27.18)

Example: Problem 27.10

A multi-plate capacitor, such as used in radios, consists of four parallel plates arranged one above the other as shown in Figure 27.5. The area of each plate is A, and the distance between adjacent plates is d. What is the capacitance of this arrangement ?

Figure 27.5. A Multi-plate Capacitor.

The multiple capacitor shown in Figure 27.5 is equivalent to three identical capacitors connected in parallel (see Figure 27.6). The capacitance of each of the three capacitors is equal and given by

(27.19)

The total capacitance of the multi-plate capacitor can be calculated using eq.(27.14):

(27.20)

Figure 27.6. Schematic of Multi-plate Capacitor shown in Figure 27.5.

Example: Problem 27.13Three capacitors, of capacitance C1 = 2.0 uF, C2 = 5.0 uF, and C3 = 7.0 uF, are initially charged to 36 V by connecting each, for a few instants, to a 36-V battery. The battery is then removed and the charged capacitors are connected in a closed series circuit, with the positive and negative terminals joined as shown in Figure 27.7. What will be the final charge on each capacitor ? What will be the voltage across the points PP' ?

Figure 27.7. Problem 27.13.

The initial charges on each of the three capacitors, q1, q2, and q3, are equal to

(27.21)

After the three capacitors are connected, the charge will redistribute itself. The charges on the three capacitors after the system settles down are equal to Q1, Q2, and Q3. Since charge is a conserved quantity, there is a relation between q1, q2, and q3, and Q1, Q2, and Q3:

(27.22)

The voltage between P and P' can be expressed in terms of C3 and Q3, or in terms of C1, C2, Q1, and Q2:

(27.23)

and

(27.24)

Using eq.(27.22) the following expressions for Q1 and Q2 can be obtained:

(27.25)

(27.26)

Substituting eq.(27.25) and eq.(27.26) into eq.(27.24) we obtain

(27.27)

Combining eq.(27.27) and eq.(27.23), Q3 can be expressed in terms of known variables:

(27.28)

Substituting the known values of the capacitance and initial charges we obtain

(27.29)

The voltage across P and P' can be found by combining eq.(27.29) and eq.(27.23):

(27.30)

The charges on capacitor 1 and capacitor 2 are equal to

(27.31)

(27.32)

27.4. DielectricsIf the space between the plates of a capacitor is filled with an insulator, the capacitance of the capacitor will chance compared to the situation in which there is vacuum between the plates. The change in the capacitance is caused by a change in the electric field between the plates. The electric field between the capacitor plates will induce dipole moments in the material between the plates. These induced dipole moments will reduce the electric field in the region between the plates. A material in which the induced dipole moment is linearly proportional to the applied electric field is called a linear dielectric. In this type of materials the total electric field between the capacitor plates E is related to the electric field Efree that would exist if no dielectric was present:

(27.33)

where [kappa] is called the dielectric constant. Since the final electric field E can never exceed the free electric field Efree, the dielectric constant [kappa] must be larger than 1.

The potential difference across a capacitor is proportional to the electric field between the plates. Since the presence of a dielectric reduces the strength of the electric field, it will also reduce the potential difference between the capacitor plates (if the total charge on the plates is kept constant):

(27.34)

The capacitance C of a system with a dielectric is inversely proportional to the potential difference between the plates, and is related to the capacitance Cfree of a capacitor with no dielectric in the following manner

(27.35)

Since [kappa] is larger than 1, the capacitance of a capacitor can be significantly increased by filling the space between the capacitor plates with a dielectric with a large [kappa].

The electric field between the two capacitor plates is the vector sum of the fields generated by the charges on the capacitor and the field generated by the surface charges on the surface of the dielectric. The electric field generated by the charges on the capacitor plates (charge density of [sigma]free) is given by

(27.36)

Assuming a charge density on the surface of the dielectric equal to [sigma]bound, the field generated by these bound charges is equal to

(27.37)

The electric field between the plates is equal to Efree/[kappa] and thus

(27.38)

Substituting eq.(27.36) and eq.(27.37) into eq.(27.38) gives

(27.39)

or

(27.40)

Example: Problem 27.19

A parallel plate capacitor of plate area A and separation distance d contains a slab of dielectric of thickness d/2 (see Figure 27.8) and dielectric constant [kappa]. The potential difference between the plates is [Delta]V.

a) In terms of the given quantities, find the electric field in the empty region of space between the plates.

b) Find the electric field inside the dielectric.

c) Find the density of bound charges on the surface of the dielectric.

Figure 27.8. Problem 27.19.

a) Suppose the electric field in the capacitor without the dielectric is equal to E0. The electric field in the dielectric, Ed, is related to the free electric field via the dielectric constant [kappa]:

(27.41)

The potential difference between the plates can be obtained by integrating the electric field between the plates:

(27.42)

The electric field in the empty region is thus equal to

(27.43)

b) The electric field in the dielectric can be found by combining eq.(27.41) and (27.43):

(27.44)

c) The free charge density [sigma]free is equal to

(27.45)

The bound charge density is related to the free charge density via the following relation

(27.46)

Combining eq.(27.45) and eq.(27.46) we obtain

(27.47)

27.5. Gauss Law in DielectricsThe electric field in an "empty" capacitor can be obtained using Gauss' law. Consider an ideal capacitor (with no fringing fields) and the integration volume shown in Figure 27.9. The area of each capacitor plate is A and the charges on the plates are +/-Q. The charge enclosed by the integration volume shown in Figure 27.9 is equal to +Q. Gauss' law states that the electric flux [Phi] through the surface of the integration volume is related to the enclosed charge:

(27.48)

If a dielectric is inserted between the plates, the electric field between the plates will change (even though the charge on the plates is kept constant). Obviously, Gauss' law, as stated in eq.(27.48), does not hold in this case. The electric field E between the capacitor plates is related to the dielectric-free field Efree:

(27.49)

where [kappa] is the dielectric constant of the material between the plates. Gauss' law can now be rewritten as

(27.50)

Gauss' law in vacuum is a special case of eq.(27.50) with [kappa] = 1.

Figure 27.9. Ideal Capacitor.

Example: Problem 27.25

A metallic sphere of radius R is surrounded by a concentric dielectric shell of inner radius R, and outer radius 3R/2. This is surrounded by a concentric, thin, metallic shell of radius 2R (see Figure 27.10). The dielectric constant of the shell is [kappa]. What is the capacitance of this contraption ?

Suppose the charge on the inner sphere is Qfree. The electric field inside the dielectric can be determined by applying Gauss' law for a dielectric (eq.(27.50)) and using as the integration volume a sphere of radius r (where R < r < 3R/2)

(27.51)

The electric field in this region is therefore given by

(27.52)

Figure 27.10. Problem 27.25.

The electric field in the region between 3R/2 and 2R can be obtained in a similar manner, and is equal to

(27.53)

Using the electric field from eq.(27.52) and eq.(27.53) we can determine the potential difference [Delta]V between the inner and outer sphere:

(27.54)

The capacitance of the system can be obtained from eq.(27.54) using the definition of the capacitance in terms of the charge Q and the potential difference [Delta]V:

(27.55)

27.6 Energy in CapacitorsThe electric potential energy of a capacitor containing no dielectric and with charge +/-Q on its plates is given by

(27.56)

where V1 and V2 are the potentials of the two plates. The electric potential energy can also be expressed in terms of the capacitance C of the capacitor

(27.57)

This formula is also correct for a capacitor with a dielectric; the properties of the dielectric enters into this formula via the capacitance C.

Example: Problem 27.40

Ten identical 5 uF capacitors are connected in parallel to a 240-V battery. The charged capacitors are then disconnected from the battery and reconnected in series, the positive terminal of each capacitor being connected to the negative terminal of the next. What is the potential difference between the negative terminal of the first capacitor and the positive terminal of the last capacitor ? If these terminals are connected via an external circuit, how much charge will flow around this circuit as the series arrangement discharges ? How much energy is released in the discharge ? Compare this charge and this energy with the charge and energy stored in the original, parallel arrangement, and explain any discrepancies.

The charge on each capacitor, after being connected to the 240-V battery, is equal to

(27.58)

The potential difference across each capacitor will remain equal to 240 V after the capacitors are connected in series. The total potential difference across the ten capacitors is thus equal to

(27.59)

If the two end terminals of the capacitor network are connected, a charge of 1.2 mC will flow from the positive terminal to the negative terminal (see Figure 27.11).

Figure 27.11. Problem 27.40.

The electric energy stored in the capacitor network before discharge is equal to

(27.60)

The energy stored in each capacitor, after being charged to 240 V, is equal to

(27.61)

Clearly no energy is lost in the process of changing the capacitor configuration from parallel to serial.

Example: Problem 27.39

Three capacitors are connected as shown in Figure 27.12. Their capacitances are C1 = 2.0 uF, C2 = 6.0 uF, and C3 = 8.0 uF. If a voltage of 200 V is applied to the two free terminals, what will be the charge on each capacitor ? What will be the electric energy of each ?

Figure 27.12. problem 27.39.

Suppose the voltage across capacitor C1 is V1, and the voltage across capacitor (C2 + C3) is V2. If the charge on capacitor C1 is equal to Q1, then the charge on the parallel capacitor is also equal to Q1. The potential difference across this system is equal to

(27.62)

The charge on capacitor 1 is thus determined by the potential difference [Delta]V

(27.63)

The voltage V23 across the capacitor (C2 + C3) is related to the charge Q1

(27.64)

The charge on capacitor C2 is equal to

(27.65)

The charge on capacitor C3 is equal to

(27.66)

The electric potential energy stored in each capacitor is equal to

(27.67)

For the three capacitors in this problem the electric potential energy is equal to

(27.68)

(27.69)

(27.70)