It's All about Electronics For Beginner's

Wednesday, September 9, 2009

capacitors

Capacitors

A capacitor or condenser is a passive electronic component consisting of a pair of conductors separated by a dielectric. When a voltage potential difference exists between the conductors, an electric field is present in the dielectric. This field stores energy and produces a mechanical force between the plates. The effect is greatest between wide, flat, parallel, narrowly separated conductors.

An ideal capacitor is characterized by a single constant value, capacitance, which is measured in farads. This is the ratio of the electric charge on each conductor to the potential difference between them. In practice, the dielectric between the plates passes a small amount of leakage current. The conductors and leads introduce an equivalent series resistance and the dielectric has an electric field strength limit resulting in a breakdown voltage.

Capacitors are widely used in electronic circuits to block the flow of direct current while allowing alternating current to pass, to filter out interference, to smooth the output of power supplies, and for many other purposes. They are used in resonant circuits in radio frequency equipment to select particular frequencies from a signal with many frequencies.

[edit] History

Battery of four Leyden jars in Museum Boerhave, Leiden.

In October 1745, Ewald Georg von Kleist of Pomerania in Germany found that charge could be stored by connecting a high voltage electrostatic generator by a wire to a volume of water in a hand-held glass jar.^[1] Von Kleist's hand and the water acted as conductors and the jar as a dielectric (although details of the mechanism were incorrectly identified at the time). Von Kleist found that after removing the generator, touching the wire resulted in a painful spark. In a letter describing the experiment, he said "I would not take a second shock for the kingdom of France."^[2] The following year, the Dutch physicist Pieter van Musschenbroek invented a similar capacitor, which was named the Leyden jar, after the University of Leyden where he worked.^[3] Daniel Gralath was the first to combine several jars in parallel into a "battery" to increase the charge storage capacity.^{[citation needed]}

Benjamin Franklin investigated the Leyden jar and proved that the charge was stored on the glass, not in the water as others had assumed.^{[citation needed]} He also created the term "battery",^[4]^[5] (as in a battery of cannon), subsequently applied to clusters of electrochemical cells.^[6] Leyden jars were later to be made by coating the inside and outside of jars with metal foil, leaving a space at the mouth to prevent arcing between the foils.^{[citation needed]} The earliest unit of capacitance was the 'jar', equivalent to about 1 nanofarad.^{[citation needed]}

Leyden jars or more powerful devices employing flat glass plates alternating with foil conductors were used exclusively up until about 1900, when the invention of wireless (radio) created a demand for standard capacitors, and the steady move to higher frequencies required capacitors with lower inductance. A more compact construction began to be used of a flexible dielectric sheet such as oiled paper sandwiched between sheets of metal foil, rolled or folded into a small package.

Early capacitors were also known as condensers, a term that is still occasionally used today. The term was first used for this purpose by Alessandro Volta in 1782, with reference to the device's ability to store a higher density of electric charge than a normal isolated conductor.^{[citation needed]}

[edit] Theory of operation

Main article: Capacitance

Charge separation in a parallel-plate capacitor causes an internal electric field. A dielectric (orange) reduces the field and increases the capacitance.

A simple demonstration of a parallel-plate capacitor

A capacitor consists of two conductors separated by a non-conductive region.^[7] The non-conductive substance is called the dielectric medium, although this may also mean a vacuum or a semiconductor depletion region chemically identical to the conductors. A capacitor is assumed to be self-contained and isolated, with no net electric charge and no influence from an external electric field. The conductors thus contain equal and opposite charges on their facing surfaces,^[8] and the dielectric contains an electric field. The capacitor is a reasonably general model for electric fields within electric circuits.

An ideal capacitor is wholly characterized by a constant capacitance 'C', defined as the ratio of charge ±'Q' on each conductor to the voltage 'V' between them:^[7]

$C = \frac{Q}{V}$

Sometimes charge buildup affects the mechanics of the capacitor, causing the capacitance to vary. In this case, capacitance is defined in terms of incremental changes:

$C = \frac{\mathrm{d}q}{\mathrm{d}v}$

In SI units, a capacitance of one farad means that one coulomb of charge on each conductor causes a voltage of one volt across the device.^[9]

[edit] Energy storage

Work must be done by an external influence to move charge between the conductors in a capacitor. When the external influence is removed, the charge separation persists and energy is stored in the electric field. If charge is later allowed to return to its equilibrium position, the energy is released. The work done in establishing the electric field, and hence the amount of energy stored, is given by:^[10]

$W = \int_0^Q V \text{d}Q' = \int_0^Q \frac{Q}{C} \text{d}Q' = {1 \over 2} {Q^2 \over C} = {1 \over 2} C V^2 = {1 \over 2} VQ.$

[edit] Current-voltage relation

The current i (t ) through a component in an electric circuit is defined as the rate of change of the charge q (t ) that has passed through it. Physical charges cannot pass through the dielectric layer of a capacitor, but rather build up in equal and opposite quantities on the electrodes: as each electron accumulates on the negative plate, one leaves the positive plate. Thus the accumulated charge on the electrodes is equal to the integral of the current, as well as being proportional to the voltage (as discussed above). As with any antiderivative, a constant of integration is added to represent the initial voltage v (t₀). This is the integral form of the capacitor equation,^[11]

$v(t) = \frac{q(t)}{C} = \frac{1}{C}\int_{t_0}^t i(\tau) \mathrm{d}\tau+v(t_0)$ .

Taking the derivative of this, and multiplying by C, yields the derivative form,^[12]

$i(t) = \frac{\mathrm{d}q(t)}{\mathrm{d}t}=C\frac{\mathrm{d}v(t)}{\mathrm{d}t}$ .

The dual of the capacitor is the inductor, which stores energy in the magnetic field rather than the electric field. Its current-voltage relation is obtained by exchanging current and voltage in the capacitor equations and replacing C with the inductance L.

[edit] DC circuits

A simple resistor-capacitor circuit demonstrates charging of a capacitor.

A series circuit containing only a resistor, a capacitor, a switch and a constant DC source of voltage V₀ is known as a charging circuit.^[13] If the capacitor is initially uncharged while the switch is open, and the switch is closed at t = 0, it follows from Kirchhoff's voltage law that

$V_0 = v_\text{resistor}(t) + v_\text{capacitor}(t) = i(t)R + \frac{1}{C}\int_0^t i(\tau)\mathrm{d}\tau.$

Taking the derivative and multiplying by C, gives a first-order differential equation,

$RC\frac{\mathrm{d}i(t)}{\mathrm{d}t} + i(t) = 0.$

At t = 0, the voltage across the capacitor is zero and the voltage across the resistor is V₀. The initial current is then i (0) =V₀ /R. With this assumption, the differential equation yields

$i(t) = \frac{V_0}{R} e^{\,^{\textstyle -t/\tau_0}}$

$v(t) = V_0 \left( 1 - e^{\,^{\textstyle -t/\tau_0}}\right),$

where τ₀ = RC is the time constant of the system.

As the capacitor reaches equilibrium with the source voltage, the voltage across the resistor and the current through the entire circuit decay exponentially. The case of discharging a charged capacitor likewise demonstrates exponential decay, but with the initial capacitor voltage replacing V₀ and the final voltage being zero.

[edit] AC circuits

Impedance, the vector sum of reactance and resistance, describes the phase difference and the ratio of amplitudes between sinusoidally varying voltage and sinusoidally varying current at a given frequency. Fourier analysis allows any signal to be constructed from a spectrum of frequencies, whence the circuit's reaction to the various frequencies may be found. The reactance and impedance of a capacitor are respectively

$X = - \frac{1}{\omega C} = - \frac{1}{2\pi f C}$

$Z = \frac{1}{j\omega C}= - \frac{j}{\omega C} = - \frac{j}{2\pi f C}$

where j is the imaginary unit and ω is the angular velocity of the sinusoidal signal. The - j phase indicates that the AC voltage V = Z I lags the AC current by 90°: the positive current phase corresponds to increasing voltage as the capacitor charges; zero current corresponds to instantaneous constant voltage, etc.

Note that impedance decreases with increasing capacitance and increasing frequency. This implies that a higher-frequency signal or a larger capacitor results in a lower voltage amplitude per current amplitude—an AC "short circuit" or AC coupling. Conversely, for very low frequencies, the reactance will be high, so that a capacitor is nearly an open circuit in AC analysis—those frequencies have been "filtered out".

Capacitors are different from resistors and inductors in that the impedance is inversely proportional to the defining characteristic, i.e. capacitance.

[edit] Parallel plate model

Dielectric is placed between two conducting plates, each of area A and with a separation of d.

The simplest capacitor consists of two parallel conductive plates separated by a dielectric with permittivity ε. The model may also be used to make qualitative predictions for other device geometries. The plates are considered to extend uniformly over an area A and a charge density ±ρ = ±Q/A exists on their surface. Assuming that the width of the plates is much greater than their separation d, the electric field near the centre of the device will be uniform with the magnitude E = ρ/ε. The voltage is defined as the line integral of the electric field between the plates

$V = \int_0^d E \mathrm{d}z = \int_0^d \frac{\rho}{\varepsilon} \mathrm{d}z = \frac{\rho d}{\varepsilon} = \frac{Qd}{\varepsilon A}.$

Solving this for C = Q/V reveals that capacitance increases with area and decreases with separation

$C = \frac{\varepsilon A}{d}$ .

The capacitance is therefore greatest in devices made from materials with a high permittivity.

[edit] Networks

[edit] Non-ideal behaviour

Capacitors deviate from the ideal capacitor equation in a number of ways. Some of these, such as leakage current and parasitic effects are linear, or can be assumed to be linear, and can be dealt with by adding virtual components to the equivalent circuit of the capacitor. The usual methods of network analysis can then be applied. In other cases, such as with breakdown voltage, the effect is non-linear and normal (i.e., linear) network analysis cannot be used, the effect must be dealt with separately. There is yet another group, which may be linear but invalidate the assumption in the analysis that capacitance is a constant. Such an example is temperature dependence.

[edit] Breakdown voltage

Main article: Breakdown voltage

Above a particular electric field, known as the dielectric strength E_ds, the dielectric in a capacitor becomes conductive. The voltage at which this occurs is called the breakdown voltage of the device, and is given by the product of the dielectric strength and the separation between the conductors,^[14]

V bd = E ds d

The maximum energy that can be stored safely in a capacitor is limited by the breakdown voltage. Due to the scaling of capacitance and breakdown voltage with dielectric thickness, all capacitors made with a particular dielectric have approximately equal maximum energy density, to the extent that the dielectric dominates their volume.^[15]

For air dielectric capacitors the breakdown field strength is of the order 10⁷ V/m and will be much less when other materials are used for the dielectric. The absolute breakdown voltage of most capacitors is nowhere near such a high number because of the very small distance between the plates. Typical ratings for capacitors used for general electronics applications range from a few volts to 100V or so. For high voltage applications physically much larger capacitors have to be used. In this field, there are a number of factors that can dramatically reduce the breakdown voltage below that to be expected by considering the breakdown field strength of the dielectric alone. For one thing, the geometry of the capacitor conductive parts (plates and connecting wires) is important. In particular, sharp edges or points hugely increase the electric field strength at that point and can lead to a local breakdown. Once this starts to happen, the breakdown will quickly "track" through the dielectric till it reaches the opposite plate and cause a short circuit.^[16]

The usual breakdown route is that the field strength becomes large enough to pull electrons in the dielectric from their atoms thus causing conduction. Other scenarios are possible, such as impurities in the dielectric, and, if the dielectric is of a crystalline nature, imperfections in the crystal structure can result in an avalanche breakdown as seen in semi-conductor devices. Breakdown voltage is also affected by pressure, humidity and temperature.^[17]

[edit] Equivalent circuit

Two equivalent circuits of a real capacitor

An ideal capacitor only stores and releases electrical energy, without dissipating any. In reality, all capacitors have imperfections within the capacitor's material that create resistance. This is specified as the equivalent series resistance or ESR of a component. This adds a real component to the impedance:

$R_\text{C} = Z + R_\text{ESR} = \frac{1}{j\omega C} + R_\text{ESR}$

As frequency approaches infinity, the capacitive impedance (or reactance) approaches zero and the ESR becomes significant. As the reactance becomes negligible, power dissipation approaches P_RMS. = V_RMS.² /R_ESR.

Similarly to ESR, the capacitor's leads add equivalent series inductance or ESL to the component. This is usually significant only at relatively high frequencies. As inductive reactance is positive and increases with frequency, above a certain frequency capacitance will be canceled by inductance. High frequency engineering involves accounting for the inductance of all connections and components.

If the conductors are separated by a material with a small conductivity rather than a perfect dielectric, then a small leakage current flows directly between them. The capacitor therefore has a finite parallel resistance,^[9] and slowly discharges over time (time may vary greatly depending on the capacitor material and quality).

[edit] Ripple current

Ripple current is the AC component of an applied source (often a switched-mode power supply) whose frequency may be constant or varying. Certain types of capacitors, such as electrolytic tantalum capacitors, usually have a rating for maximum ripple current (both in frequency and magnitude). This ripple current can cause damaging heat to be generated within the capacitor due to the current flow across resistive imperfections in the materials used within the capacitor, more commonly referred to as equivalent series resistance (ESR). For example electrolytic tantalum capacitors are limited by ripple current and generally have the highest ESR ratings in the capacitor family, while ceramic capacitors generally have no ripple current limitation and have some of the lowest ESR ratings.

[edit] Instability of capacitance

The capacitance of certain capacitors decreases as the component ages. In ceramic capacitors, this is caused by degradation of the dielectric. The type of dielectric and the ambient operating and storage temperatures are the most significant aging factors, while the operating voltage has a smaller effect. The aging process may be reversed by heating the component above the Curie point. Aging is fastest near the beginning of life of the component, and the device stabilizes over time.^[18] Electrolytic capacitors age as the electrolyte evaporates. In contrast with ceramic capacitors, this occurs towards the end of life of the component.

Temperature dependence of capacitance is usually expressed in parts per million (ppm) per °C. It can usually be taken as a broadly linear function but can be noticeably non-linear at the temperature extremes. The temperature coefficient can be either positive or negative, sometimes even amongst different samples of the same type. In other words, the spread in the range of temperature coefficients can encompass zero. See the data sheet in the leakage current section above for an example.

Capacitors, especially older components, can absorb sound waves resulting in a microphonic effect. Vibration moves the plates, causing the capacitance to vary, in turn inducing AC current. Some dielectrics also generate piezoelectricity. The resulting interference is especially problematic in audio applications, potentially causing feedback or unintended recording. In the reverse microphonic effect, the varying electric field between the capacitor plates exerts a physical force, moving them as a speaker. This can generate audible sound, but drains energy and stresses the dielectric and the electrolyte, if any.

[edit] Capacitor types

Main article: Types of capacitor

Practical capacitors are available commercially in many different forms. The type of internal dielectric, the structure of the plates and the device packaging all strongly affect the characteristics of the capacitor, and its applications.

[edit] Dielectric materials

Capacitor materials. From left: multilayer ceramic, ceramic disc, multilayer polyester film, tubular ceramic, polystyrene, metalized polyester film, aluminum electrolytic. Major scale divisions are in centimetres.

Most types of capacitor include a dielectric spacer, which increases their capacitance. These dielectrics are most often insulators. However, low capacitance devices are available with a vacuum between their plates, which allows extremely high voltage operation and low losses. Variable capacitors with their plates open to the atmosphere were commonly used in radio tuning circuits. Later designs use polymer foil dielectric between the moving and stationary plates, with no significant air space between them.

Several solid dielectrics are available, including paper, plastic, glass, mica and ceramic materials. Paper was used extensively in older devices and offers relatively high voltage performance. However, it is susceptible to water absorption, and has been largely replaced by plastic film capacitors. Plastics offer better stability and aging performance, which makes them useful in timer circuits, although they may be limited to low operating temperatures and frequencies. Ceramic capacitors are generally small, cheap and useful for high frequency applications, although their capacitance varies strongly with voltage, and they age poorly. They are broadly categorized as class 1 dielectrics, which have predictable variation of capacitance with temperature or class 2 dielectrics, which can operate at higher voltage. Glass and mica capacitors are extremely reliable, stable and tolerant to high temperatures and voltages, but are too expensive for most mainstream applications. Electrolytic capacitors and supercapacitors are used to store small and larger amounts of energy, respectively, ceramic capacitors are often used in resonators, and parasitic capacitance occurs in circuits wherever the simple conductor-insulator-conductor sequence is formed unintentionally.

Electrolytic capacitors use an aluminum or tantalum plate with an oxide dielectric layer. The second electrode is a liquid electrolyte, connected to the circuit by another foil plate. Electrolytic capacitors offer very high capacitance but suffer from poor tolerances, high instability, gradual loss of capacitance especially when subjected to heat, and high leakage current. The conductivity of the electrolyte drops at low temperatures, which increases equivalent series resistance. While widely used for power-supply conditioning, poor high-frequency characteristics make them unsuitable for many applications. Tantalum capacitors offer better frequency and temperature characteristics than aluminum, but higher dielectric absorption and leakage.^[19] OS-CON (or OC-CON) capacitors are a polymerized organic semiconductor solid-electrolyte type that offer longer life at higher cost than standard electrolytic capacitors.

Several other types of capacitor are available for specialist applications. supercapacitors store large amounts of energy. Supercapacitors made from carbon aerogel, carbon nanotubes, or highly porous electrode materials offer extremely high capacitance (as much as 3000 farads) and can be used in some applications instead of rechargeable batteries. Alternating current capacitors are specifically designed to work on line (mains) voltage AC power circuits. They are commonly used in electric motor circuits and are often designed to handle large currents, so they tend to be physically large. They are usually ruggedly packaged, often in metal cases that can be easily grounded/earthed. They also are designed with direct current breakdown voltages of at least five times the maximum AC voltage.

[edit] Structure

Capacitor packages: SMD ceramic at top left; SMD tantalum at bottom left; through-hole tantalum at top right; through-hole electrolytic at bottom right. Major scale divisions are cm.

The arrangement of plates and dielectric has many variations depending on the desired ratings of the capacitor. For small values of capacitance (microfarads and less), ceramic disks use metallic coatings, with wire leads bonded to the coating. Larger values can be made by multiple stacks of plates and disks. Larger value capacitors usually use a metal foil or metal film layer deposited on the surface of a dielectric film to make the plates, and a dielectric film of impregnated paper or plastic – these are rolled up to save space. To reduce the series resistance and inductance for long plates, the plates and dielectric are staggered so that connection is made at the common edge of the rolled-up plates, not at the ends of the foil or metalized film strips that comprise the plates.

The assembly is encased to prevent moisture entering the dielectric – early radio equipment used a cardboard tube sealed with wax. Modern paper or film dielectric capacitors are dipped in a hard thermoplastic. Large capacitors for high-voltage use may have the roll form compressed to fit into a rectangular metal case, with bolted terminals and bushings for connections. The dielectric in larger capacitors is often impregnated with a liquid to improve its properties.

Capacitors may have their connecting leads arranged in many configurations, for example axially or radially. "Axial" means that the leads are on a common axis, typically the axis of the capacitor's cylindrical body – the leads extend from opposite ends. Radial leads might more accurately be referred to as tandem; they are rarely actually aligned along radii of the body's circle, so the term is inexact, although universal. The leads (until bent!) are usually in planes parallel to that of the flat body of the capacitor, and extend in the same direction; they are often parallel as manufactured.

Small, cheap discoidal ceramic capacitors have existed since the 1930s, and remain in widespread use. Since the 1980s, surface mount packages for capacitors have been widely used. These packages are extremely small and lack connecting leads, allowing them to be soldered directly onto the surface of printed circuit boards. Surface mount components avoid undesirable high-frequency effects due to the leads and simplify automated assembly, although manual handling is made difficult due to their small size.

Mechanically controlled variable capacitors allow the plate spacing to be adjusted, for example by rotating or sliding a set of movable plates into alignment with a set of stationary plates. Low cost variable capacitors squeeze together alternating layers of aluminum and plastic with a screw. Electrical control of capacitance is achievable with varactors (or varicaps), which are reverse-biased semiconductor diodes whose depletion region width varies with applied voltage. They are used in phase-locked loops, amongst other applications.

[edit] Applications

Main article: Applications of capacitors

Capacitors have many uses in electronic and electrical systems. They are so common that it is a rare electrical product that does not include at least one for some purpose.

[edit] System Energy Storage

A capacitor can store electric energy when disconnected from its charging circuit, so it can be used like a temporary battery. Capacitors are commonly used in electronic devices to maintain power supply while batteries are being changed. (This prevents loss of information in volatile memory.)

In car audio systems, large capacitors store energy for the amplifier to use on demand.

UPSes can be equipped with maintenance-free capacitors to extend service life.^[20]

**Capacitor symbols**
Capacitor	Polarized capacitors	Variable capacitor

[edit] Pulsed power and weapons

Groups of large, specially constructed, low-inductance high-voltage capacitors (capacitor banks) are used to supply huge pulses of current for many pulsed power applications. These include electromagnetic forming, Marx generators, pulsed lasers (especially TEA lasers), pulse forming networks, radar, fusion research, and particle accelerators.

Large capacitor banks (reservoir) are used as energy sources for the exploding-bridgewire detonators or slapper detonators in nuclear weapons and other specialty weapons. Experimental work is under way using banks of capacitors as power sources for electromagnetic armour and electromagnetic railguns and coilguns.

[edit] Power conditioning

Reservoir capacitors are used in power supplies where they smooth the output of a full or half wave rectifier. They can also be used in charge pump circuits as the energy storage element in the generation of higher voltages than the input voltage.

Capacitors are connected in parallel with the power circuits of most electronic devices and larger systems (such as factories) to shunt away and conceal current fluctuations from the primary power source to provide a "clean" power supply for signal or control circuits. Audio equipment, for example, uses several capacitors in this way, to shunt away power line hum before it gets into the signal circuitry. The capacitors act as a local reserve for the DC power source, and bypass AC currents from the power supply. This is used in car audio applications, when a stiffening capacitor compensates for the inductance and resistance of the leads to the lead-acid car battery.

[edit] Power factor correction

In electric power distribution, capacitors are used for power factor correction. Such capacitors often come as three capacitors connected as a three phase load. Usually, the values of these capacitors are given not in farads but rather as a reactive power in volt-amperes reactive (VAr). The purpose is to counteract inductive loading from devices like electric motors and transmission lines to make the load appear to be mostly resistive. Individual motor or lamp loads may have capacitors for power factor correction, or larger sets of capacitors (usually with automatic switching devices) may be installed at a load center within a building or in a large utility substation.

[edit] Supression and coupling

[edit] Signal coupling

Main article: capacitive coupling

Because capacitors pass AC but block DC signals (when charged up to the applied dc voltage), they are often used to separate the AC and DC components of a signal. This method is known as AC coupling or "capacitive coupling". Here, a large value of capacitance, whose value need not be accurately controlled, but whose reactance is small at the signal frequency, is employed.

[edit] Decoupling

Main article: decoupling capacitor

A decoupling capacitor is a capacitor used to protect one part of a circuit from the effect of another, for instance to suppress noise or transients. Noise caused by other circuit elements is shunted through the capacitor, reducing the effect they have on the rest of the circuit. It is most commonly used between the power supply and ground. An alternative name is bypass capacitor as it is used to bypass the power supply or other high impedance component of a circuit.

[edit] Noise filters and snubbers

When an inductive circuit is opened, the current through the inductance collapses quickly, creating a large voltage across the open circuit of the switch or relay. If the inductance is large enough, the energy will generate a spark, causing the contact points to oxidize, deteriorate, or sometimes weld together, or destroying a solid-state switch. A snubber capacitor across the newly opened circuit creates a path for this impulse to bypass the contact points, thereby preserving their life; these were commonly found in contact breaker ignition systems, for instance. Similarly, in smaller scale circuits, the spark may not be enough to damage the switch but will still radiate undesirable radio frequency interference (RFI), which a filter capacitor absorbs. Snubber capacitors are usually employed with a low-value resistor in series, to dissipate energy and minimize RFI. Such resistor-capacitor combinations are available in a single package.

Capacitors are also used in parallel to interrupt units of a high-voltage circuit breaker in order to equally distribute the voltage between these units. In this case they are called grading capacitors.

In schematic diagrams, a capacitor used primarily for DC charge storage is often drawn vertically in circuit diagrams with the lower, more negative, plate drawn as an arc. The straight plate indicates the positive terminal of the device, if it is polarized (see electrolytic capacitor).

[edit] Motor starters

Main article: motor capacitor

In single phase squirrel cage motors, the primary winding within the motor housing isn't capable of starting a rotational motion on the rotor, but is capable of sustaining one. To start the motor, a secondary winding is used in series with a non-polarized starting capacitor to introduce a lag in the sinusoidal current through the starting winding. When the secondary winding is placed at an angle with respect to the primary winding, a rotating electric field is created. The force of the rotational field is not constant, but is sufficient to start the rotor spinning. When the rotor comes close to operating speed, a centrifugal switch (or current-sensitive relay in series with the main winding) disconnects the capacitor. The start capacitor is typically mounted to the side of the motor housing. These are called capacitor-start motors, and have relatively high starting torque. There are also capacitor-run induction motors which have a permanently-connected phase-shifting capacitor in series with a second winding. The motor is much like a two-phase induction motor.

Motor-starting capacitors are typically non-polarized electrolytic types, while running capacitors are conventional paper or plastic film dielectric types.

[edit] Signal processing

The energy stored in a capacitor can be used to represent information, either in binary form, as in DRAMs, or in analogue form, as in analog sampled filters and CCDs. Capacitors can be used in analog circuits as components of integrators or more complex filters and in negative feedback loop stabilization. Signal processing circuits also use capacitors to integrate a current signal.

[edit] Tuned circuits

Capacitors and inductors are applied together in tuned circuits to select information in particular frequency bands. For example, radio receivers rely on variable capacitors to tune the station frequency. Speakers use passive analog crossovers, and analog equalizers use capacitors to select different audio bands.

The resonant frequency f of a tuned circuit is a function of the inductance (L) and capacitance (C) in series, and is given by:

$f = \frac{1}{2 \pi \sqrt{LC}}$

where L is in henries and C is in farads.

[edit] Sensing

Most capacitors are designed to maintain a fixed physical structure. However, various factors can change the structure of the capacitor, and the resulting change in capacitance can be used to sense those factors.

Changing the dielectric:

The effects of varying the physical and/or electrical characteristics of the dielectric can be used for sensing purposes. Capacitors with an exposed and porous dielectric can be used to measure humidity in air. Capacitors are used to accurately measure the fuel level in airplanes; as the fuel covers more of a pair of plates, the circuit capacitance increases.

Changing the distance between the plates:

Capacitors with a flexible plate can be used to measure strain or pressure. Industrial pressure transmitters used for process control use pressure-sensing diaphragms, which form a capacitor plate of an oscillator circuit. Capacitors are used as the sensor in condenser microphones, where one plate is moved by air pressure, relative to the fixed position of the other plate. Some accelerometers use MEMS capacitors etched on a chip to measure the magnitude and direction of the acceleration vector. They are used to detect changes in acceleration, e.g. as tilt sensors or to detect free fall, as sensors triggering airbag deployment, and in many other applications. Some fingerprint sensors use capacitors. Additionally, a user can adjust the pitch of a theremin musical instrument by moving his hand since this changes the effective capacitance between the user's hand and the antenna.

Changing the effective area of the plates:

Capacitive touch switches are now used on many consumer electronic products.

[edit] Hazards and safety

Lichtenberg figures are produced by inducing a capacitor failure in a capacitor with a solid dielectric.

Capacitors may retain a charge long after power is removed from a circuit; this charge can cause shocks or damage to connected equipment. For example, even a seemingly innocuous device such as a disposable camera flash unit powered by a 1.5 volt AA battery contains a capacitor which may be charged to over 300 volts. This is easily capable of delivering a shock. Service procedures for electronic devices usually include instructions to discharge large or high-voltage capacitors. Capacitors may also have built-in discharge resistors to dissipate stored energy to a safe level within a few seconds after power is removed. High-voltage capacitors are stored with the terminals shorted, as protection from potentially dangerous voltages due to dielectric absorption.

Some old, large oil-filled capacitors contain polychlorinated biphenyls (PCBs). It is known that waste PCBs can leak into groundwater under landfills. Capacitors containing PCB were labelled as containing "Askarel" and several other trade names. PCB-filled capacitors are found in very old (pre 1975) fluorescent lamp ballasts, and other applications.

High-voltage capacitors may catastrophically fail when subjected to voltages or currents beyond their rating, or as they reach their normal end of life. Dielectric or metal interconnection failures may create arcing that vaporizes dielectric fluid, resulting in case bulging, rupture, or even an explosion. Capacitors used in RF or sustained high-current applications can overheat, especially in the center of the capacitor rolls. Capacitors used within high-energy capacitor banks can violently explode when a short in one capacitor causes sudden dumping of energy stored in the rest of the bank into the failing unit. High voltage vacuum capacitors can generate soft X-rays even during normal operation. Proper containment, fusing, and preventive maintenance can help to minimize these hazards.

High-voltage capacitors can benefit from a pre-charge to limit in-rush currents at power-up of HVDC circuits. This will extend the life of the component and may mitigate high-voltage hazards.

[edit]

Monday, September 7, 2009

Thin film - basics

Thin films are thin material layers ranging from fractions of a nanometre (less than the width of an atom, or monolayer) to several micrometres in thickness. Electronic semiconductor devices and optical coatings are the main applications benefiting from thin film construction.

A familiar application of thin films is the household mirror which typically has a thin metal coating on the back of a sheet of glass to form a reflective interface. The process of silvering was once commonly used to produce mirrors. A very thin film coating (less than a nanometer) is used to produce two-way mirrors.

The performance of optical coatings (e.g. antireflective, or AR, coatings) are typically enhanced when the thin film coating consists of multiple layers having varying thicknesses and refractive indices. Similarly, a periodic structure of alternating thin films of different materials may collectively form a so-called superlattice which exploits the phenomenon of quantum confinement by restricting electronic phenomena to two-dimensions.

Work is being done with ferromagnetic thin films for use as computer memory. It is also being applied to pharmaceuticals, via thin film drug delivery. Thin-films are used to produce thin-film batteries.[1]

Ceramic thin films are in wide use. The relatively high hardness and inertness of ceramic materials make this type of thin coating of interest for protection of substrate materials against corrosion, oxidation and wear. In particular, the use of such coatings on cutting tools can extend the life of these items by several orders of magnitude.

Research is being done on a new class of thin film inorganic oxide materials, called amorphous heavy-metal cation multicomponent oxide, which could be used to make transparent transistors that are inexpensive, stable, and environmentally benign.[2]
Contents
[hide]

* 1 History
* 2 Deposition
o 2.1 Chemical deposition
o 2.2 Physical deposition
o 2.3 Other deposition processes
* 3 Thin-film photovoltaic cells
* 4 See also
* 5 References
o 5.1 Further reading
o 5.2 Footnotes

Deposition

The act of applying a thin film to a surface is known as thin-film deposition.

Thin-film deposition is any technique for depositing a thin film of material onto a substrate or onto previously deposited layers. "Thin" is a relative term, but most deposition techniques allow layer thickness to be controlled within a few tens of nanometers, and some (molecular beam epitaxy) allow single layers of atoms to be deposited at a time.

It is useful in the manufacture of optics (for reflective or anti-reflective coatings, for instance), electronics (layers of insulators, semiconductors, and conductors form integrated circuits), packaging (i.e., aluminum-coated PET film), and in contemporary art (see the work of Larry Bell). Similar processes are sometimes used where thickness is not important: for instance, the purification of copper by electroplating, and the deposition of silicon and enriched uranium by a CVD-like process after gas-phase processing.

Deposition techniques fall into two broad categories, depending on whether the process is primarily chemical or physical.

Chemical deposition

Here, a fluid precursor undergoes a chemical change at a solid surface, leaving a solid layer. An everyday example is the formation of soot on a cool object when it is placed inside a flame. Since the fluid surrounds the solid object, deposition happens on every surface, with little regard to direction; thin films from chemical deposition techniques tend to be conformal, rather than directional.

Chemical deposition is further categorized by the phase of the precursor:

* Plating relies on liquid precursors, often a solution of water with a salt of the metal to be deposited. Some plating processes are driven entirely by reagents in the solution (usually for noble metals), but by far the most commercially important process is electroplating. It was not commonly used in semiconductor processing for many years, but has seen a resurgence with more widespread use of chemical-mechanical polishing techniques.

* Chemical solution deposition (CSD) uses a liquid precursor, usually a solution of organometallic powders dissolved in an organic solvent. This is a relatively inexpensive, simple thin film process that is able to produce stoichiometrically accurate crystalline phases.

* Chemical vapor deposition (CVD) generally uses a gas-phase precursor, often a halide or hydride of the element to be deposited. In the case of MOCVD, an organometallic gas is used. Commercial techniques often use very low pressures of precursor gas.
o Plasma enhanced CVD (PECVD) uses an ionized vapor, or plasma, as a precursor. Unlike the soot example above, commercial PECVD relies on electromagnetic means (electric current, microwave excitation), rather than a chemical reaction, to produce a plasma.

Physical deposition

Physical deposition uses mechanical or thermodynamic means to produce a thin film of solid. An everyday example is the formation of frost. Since most engineering materials are held together by relatively high energies, and chemical reactions are not used to store these energies, commercial physical deposition systems tend to require a low-pressure vapor environment to function properly; most can be classified as physical vapor deposition (PVD).

The material to be deposited is placed in an energetic, entropic environment, so that particles of material escape its surface. Facing this source is a cooler surface which draws energy from these particles as they arrive, allowing them to form a solid layer. The whole system is kept in a vacuum deposition chamber, to allow the particles to travel as freely as possible. Since particles tend to follow a straight path, films deposited by physical means are commonly directional, rather than conformal.

Examples of physical deposition include:

* A thermal evaporator uses an electric resistance heater to melt the material and raise its vapor pressure to a useful range. This is done in a high vacuum, both to allow the vapor to reach the substrate without reacting with or scattering against other gas-phase atoms in the chamber, and reduce the incorporation of impurities from the residual gas in the vacuum chamber. Obviously, only materials with a much higher vapor pressure than the heating element can be deposited without contamination of the film. Molecular beam epitaxy is a particular sophisticated form of thermal evaporation.
o An electron beam evaporator fires a high-energy beam from an electron gun to boil a small spot of material; since the heating is not uniform, lower vapor pressure materials can be deposited. The beam is usually bent through an angle of 270° in order to ensure that the gun filament is not directly exposed to the evaporant flux. Typical deposition rates for electron beam evaporation range from 1 to 10 nanometers per second.

* Sputtering relies on a plasma (usually a noble gas, such as argon) to knock material from a "target" a few atoms at a time. The target can be kept at a relatively low temperature, since the process is not one of evaporation, making this one of the most flexible deposition techniques. It is especially useful for compounds or mixtures, where different components would otherwise tend to evaporate at different rates. Note, sputtering's step coverage is more or less conformal.It is also widely used in the optical media. The manufacturing of all formats of CD, DVD, and BD are basically done with the help of this technique. It is a fast technique and also it provides a good thickness control. Now a days in sputtering, Nitrogen and Oxygen gases are also being used.

* Pulsed laser deposition systems work by an ablation process. Pulses of focused laser light vaporize the surface of the target material and convert it to plasma; this plasma usually reverts to a gas before it reaches the substrate.

* Cathodic arc deposition (arc-PVD) which is a kind of ion beam deposition where an electrical arc is created that literally blasts ions from the cathode. The arc has an extremely high power density resulting in a high level of ionization (30-100%), multiply charged ions, neutral particles, clusters and macro-particles (droplets). If a reactive gas is introduced during the evaporation process, dissociation, ionization and excitation can occur during interaction with the ion flux and a compound film will be deposited.

Other deposition processes

Some methods fall outside these two categories, relying on a mixture of chemical and physical means:

* In reactive sputtering, a small amount of some non-noble gas such as oxygen or nitrogen is mixed with the plasma-forming gas. After the material is sputtered from the target, it reacts with this gas, so that the deposited film is a different material, i.e. an oxide or nitride of the target material.

* In molecular beam epitaxy (MBE), slow streams of an element can be directed at the substrate, so that material deposits one atomic layer at a time. Compounds such as gallium arsenide are usually deposited by repeatedly applying a layer of one element (i.e., gallium), then a layer of the other (i.e., As), so that the process is chemical, as well as physical. The beam of material can be generated by either physical means (that is, by a furnace) or by a chemical reaction (chemical beam epitaxy).

* In topotaxy, a specialized technique similar to epitaxy, thin film crystal growth occurs in three dimensions due to the crystal structure similarities (either heterotopotaxy or homotopotaxy) between the substrate crystal and the growing thin film material.[3]

Thin-film photovoltaic cells

Thin-film technologies are also being developed as a means of substantially reducing the cost of photovoltaic (PV) systems. The rationale for this is that thin-film modules are cheaper to manufacture owing to their reduced material costs, energy costs, handling costs and capital costs. This is especially represented in the use of printed electronics (roll-to-roll) processes.

Thin films belong to the second and third photovoltaic cell generations.

References

* Anders, Andre (editor) "Handbook of Plasma Immersion Ion Implantation and Deposition" (2000) Wiley-Interscience ISBN 0-4712-4698-0
* Bach, Hans and Dieter Krause (editors) "Thin Films on Glass" (2003) Springer-Verlag ISBN 3-540-58597-4
* Birkholz, M., with contributions by Fewster, P. F. and Genzel, C. "Thin Film Analysis by X-ray Scattering" (2006) Wiley-VCH, Weinheim ISBN 3-527-31052-5
* Bunshah, Roitan F (editor). "Handbook of Deposition Technologies for Films and Coatings", second edition (1994)
* Glaser, Hans Joachim "Large Area Glass Coating" (2000) Von Ardenne Anlagentechnik GmbH ISBN 3-00-004953-3
* Glocker,and I. Shah (editors), "Handbook of Thin Film Process Technology", Vol.1&2 (2002) Institute of Physics ISBN 0 7503 0833 8 (2 vol. set)
* Mahan, John E. "Physical Vapor Deposition of Thin Films" (2000) John Wiley & Sons ISBN 0-471-33001-9
* Mattox, Donald M. "Handbook of Physical Vapor Deposition (PVD) Processing" (1998) Noyes Publications ISBN 0-8155-1422-0
* Mattox, Donald M. "The Foundations of Vacuum Coating Technology" (2003) Noyes Publications ISBN 0-8155-1495-6
* Mattox, Donald M. and Vivivenne Harwood Mattox (editors) "50 Years of Vacuum Coating Technology and the Growth of the Society of Vacuum Coaters" (2007), Society of Vacuum Coaters ISBN 978-1-878068-27-9
* Westwood, William D. "Sputter Deposition", AVS Education Committee Book Series, Vol. 2 (2003) AVS ISBN 0-7354-0105-5
* Willey, Ronald R. "Practical Monitoring and Control of Optical Thin Films (2007)" Willey Optical, Consultants ISBN 978-6151-3760-5
* Willey, Ronald R. "Practical Equipment, Materials, and Processes for Optical Thin Films" (2007) Willey Optical, Consultants ISBN 978-6151-4397-2
* Ohring, Milton "Materials Science of Thin Films: Deposition and Structure" 2nd edition (2002) Elsevier, Inc. ISBN 978-0-12-524975-1
s
1. ^ http://www.sciengineeredmaterials.com
2. ^ http://www.eurekalert.org/pub_releases/2004-12/osu-mam122804.php
3. ^ http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=1&f=G&l=50&co1=AND&d=PTXT&s1=zurbuchen.INNM.&OS=IN/zurbuchen&RS=IN/zurbuchen

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Resistors

RESISTANCE
The resistor is an electrical device whose primary function is to introduce resistance to the flow of electric current. The magnitude of opposition to the flow of current is called the resistance of the resistor. A larger resistance value indicates a greater opposition to current flow. The resistance is measured in ohms. An ohm is the resistance that arises when a current of one ampere is passed through a resistor subjected to one volt across its terminals. The various uses of resistors include setting biases, controlling gain, fixing time constants, matching and loading circuits, voltage division, and heat generation.
Where
ρ is the resistivity of the resistor material (W· cm),
l is the length of the resistor along direction of current flow (cm), and
A is the cross-sectional area perpendicular to current flow (cm2)
Resistor Power Rating:-
When current passes through a resistor, electrical energy is lost in the resistor in the form of heat and the greater this current flow the hotter the resistor gets. A resistor can be used at any combination of voltage (within reason) and current as long as its power rating is not exceeded and the power rating of a resistor indicates how much power the resistor can convert into heat without damage to itself.
Fixed resistors: -
Carbon composite resistors: Carbon resistors are the most common type of composition resistors. Their resistive element is manufactured from a mixture of finely ground carbon dust (graphite) and a non-conducting ceramic (clay) powder. The ratio of carbon to ceramic determines the overall resistive value of the mixture and the higher this ratio the lower the resistance. The mixture is moulded into a cylindrical shape and metal wires are attached to each end to provide the electrical connection before being coated with an outer insulating material.
Carbon composite resistors are prefixed with a "CR" notation (eg CR10kΩ) and are available in E6 (±20% tolerance (accuracy)), E12 (±10% tolerance) and E24 (±5% & ±2% tolerance) packages with power ratings of 0.125 (1/4) W to 2W.
Film Resistors: -The generic term "Film resistor" consists of Metal Film, Carbon Film and Metal Oxide Film resistors, generally made by depositing pure metals, such as nickel, or an oxide film, such as tin-oxide, onto an insulating ceramic rod or substrate. The resistance value of the resistor is controlled by increasing the desired thickness of the film and then by laser cutting a spiral helix groove type pattern into the film. This method of manufacture allows for closer tolerance resistors (1% or less) as compared to the simpler carbon composition types. The tolerance of a resistor is the difference between the preffered value (i.e., 100 ohms) and its actual manufactured value i.e., 103.6 ohms, and is expressed as a percentage, for example 5%, 10% etc, and in our example the actual tolerance is 3.6%. Film type resistors also achiever a much higher maximum ohmic value compared to other types and values in excess of 10MΩ (10 Million Ω´s) are available.
Wire wound Resistors: Wire wound resistor, is made from winding a metal alloy wire (Nichrome) or similar wire onto an insulating ceramic former. These types of resistors are generally only available in low ohmic high precision values (from 0.01 to 100kΩ) due to the gauge of the wire and number of turns possible on the former. They are also able to handle much higher currents than other resistor of the same physical size and power ratings in excess of 300 Watts are available. These high power resistors are molded or pressed into an aluminum heat sink body with fins attached to increase their surface area and promote heat loss. These types of resistors are called "Chassis Mounted Resistors". They are designed to be physically mounted to heat sinks or metal plates to further dissipate the generated heat increasing their current carrying capabilities.

The heater elements of an electric fire use wire wound resistor principles converting current into heat with each element dissipating 1000 Because the wire is wound into a coil, it acts like an inductor as well as exhibiting resistance and effects the way the resistor behaves in a.c. circuits at high frequencies and above. The length of the actual resistance path in the resistor and the leads contributes inductance in series with the "apparent" d.c. resistance resulting in an overall impedance path Z. Impedance (Z) is the combined effect of resistance (R) and inductance (X), measured in ohms and for a series a.c. circuit is given as, Z2 = R2 + X2.
When used in a.c. circuits this inductance value changes with frequency (inductive reactance, XL = 2πƒL) and therefore, the overall value of the resistor changes. Inductive reactance increases with frequency but is zero at d.c. (zero frequency). Then, wire wound resistors must not be designed into a.c. or amplifier type circuits where the frequency across the resistor changes. However, special non-inductive wirewound resistors are available.

Metal oxide resistor: -
A resistor is a component of an electric circuit that produces heat while offering opposition, or resistance, to the flow of electricity. A resistor can introduce resistance into an electric circuit. Resistors are primarily used for protection, operation or current control. The resistor materials are generally classified into metallic resistor materials, metal oxide resistor materials, and non-metallic resistor materials. Of these materials, the metal oxide resistor materials have heat resistances and energy breakdowns for absorbing a high electrical energy, which are higher than those of other materials.

Variable Resistors
There are two general ways in which variable resistors are used. One is the variable resistor which value is easily changed, like the volume adjustment of Radio. The other is semi-fixed resistor that is not meant to be adjusted by anyone but a technician. It is used to adjust the operating condition of the circuit by the technician. Semi-fixed resistors are used to compensate for the inaccuracies of the resistors, and to fine-tune a circuit. The rotation angle of the variable resistor is usually about 300 degrees. Some variable resistors must be turned many times to use the whole range of resistance they offer. This allows for very precise adjustments of their value. These are called "Potentiometers" or "Trimmer Potentiometers."

\Special Type of Resistor

(1)Thermistor (Thermally sensitive resistor)
Nonlinear resistors - a. NTC, b. PTC

The resistance value of the thermistor changes according to temperature.
NTC (Negative Temperature Coefficient Thermistor): With this type, the resistance value decreases continuously as the temperature rises.
PTC (Positive Temperature Coefficient Thermistor): With this type, the resistance value increases suddenly when the temperature rises above a specific point.
CTR (Critical Temperature Resister Thermistor) : With this type, the resistance value decreases suddenly when the temperature rises above a specific point.
The NTC type is used for the temperature control.The relation between the temperature and the resistance value of the NTC type can be calculated using the following formula.
(2) Resistor Array
This resistor is called a Single-In-Line (SIL) resistor network. It is made with many resistors of the same value, all in one package. One side of each resistor is connected with one side of all the other resistors inside. One example of its use would be to control the current in a circuit powering many light emitting diodes (LEDs)
.
(3) LDR: As the name implies, light dependent resistor (LDR), is a device whose the resistance changes in response on the amount of light falling in it. An LDR’s resistance value in the presence of strong light is just a few ohms , but in absence of light , the value can be tens of megaohms. It is an important to note that they not linear in their response. The basic material from which the LDR can be prepared is calcium sulphide or lead sulphide. Since LDR are fairly slow in their response to changing in light ,circuit which required a high speed response , such as optical communication system , use photodiode or phototransistor .
An LDR is an input transducer (sensor) which converts brightness (light) to resistance. It is made from cadmium sulphide (CdS) and the resistance decreases as the brightness of light falling on the LDR increases.
Darkness: maximum resistance, about 1M . Very bright light: minimum resistance, about 100 .

MATLAB BOOKS

A Guide to MATLAB For Beginners and Experienced Users
A Guide to MATLAB Object-Oriented Programming
Adaptive Filtering Primer with MATLAB - Poularikas and Ramadan
Advanced Mathematics and Mechanics Applications Using MATLAB, Third Edition
Algorithm Collections for Digital Signal Processing Applications using Matlab -
An Introduction to Programming and Numerical Methods in MATLAB -
An Introduction to Scientific Computing Twelve Computational Projects Solved with Matlab
Antenna and EM Modeling with MATLAB - Sergey N. Makarov.zip
Applied Numerical Methods Using MATLAB - Yang Cao Chung and Morris
Applied Statistics Using SPSS, STATISTICA, MATLAB and R - Joaquim P. Marques
Atmospheric and Space Flight Dynamics; Modeling and Simulation with MATLABR and Simulink
Basics of MATLAB and Beyond.zip
Biosignal and Biomedical Image Processing MATLAB based Applications - John L. Semmlow
Business, Economics, and Finance with Matlab, GIS, and Simulation Models
Chemical Process Control a First Course with Matlab - P.C. Chau
Circuit Analysis I with MATLAB -17Circuit Analysis II with MATLAB - Steven T. Karris
Circuits, Signals, and Systems for Bioengineers A MATLAB-Based Introduction
Classical Feedback Control with MATLAB
Classification Parameter Estimation & State Estimation An Engg Approach Using MATLAB
Computational Colour Science Using MATLAB - Stephen Westland & Caterina Ripamonti
Computational Mathematics Models Methods and Analysis with Matlab - Robert E. White
Computational Statistics Handbook with MATLAB - Martinez & Martinez.zip
Contemporary Communication Systems using Matlab - Proakis and Salehi
Contemporary Optical Image Processing With Matlab
Digital Circuit Analysis and Design with Simulink Modeling - Steven T. Karris
Digital Image Processing Using Matlab - Gonzalez Woods & Eddins
Digital Signal and Image Processing Using MATLAB - Gerard Blanchet & Maurice Charbit
Digital Signal Processing - Computer Based Approach - Sanjit K. Mitra
Digital Signal Processing Using Matlab V4 - Ingle and Proakis
Dynamic simulation of Electric Machinery using MATLAB.zip
Electronic Devices and Amplifier Circuits with MATLAB Applications - Steven T. Karris
Electronics and Circuit Analysis using MATLAB
Elementary Mathematical and Computational Tools for Electrical and Computer Engineers Using MATLAB
Embedded control systems in C-C++. An introduction for software developers using MATLAB
Embedded Image Processing on the TMS320C6000 DSP Examples in Code Composer Studio and MATLAB
Engineering Analysis, Interactive Methods and Programs With FORTRAN QuickBASIC MATLAB and Mathematica
Engineering and Scientific Computations Using MATLAB - Sergey E. Lyshevski
Environmental Modeling Using MATLAB
Essential.MATLAB.for.Engineers.and.Scientists.3rd. Edition.Mar.2007
Evolutionary Intelligence; An Introduction to Theory and Applications with Matlab
Exploratory Data Analysis with MATLAB - Martinez and Martinez
Finite Element Method using MATLAB - Kwon and Bang
Fundamentals of Electromagnetics with Matlab - Lonngren & Savov
Getting Started with Matlab 7 -46Graphics.And.Guis.With.MATLAB,.3rd.Ed.zip
Introduction to Fuzzy Logic using MatLab - Sivanandam Sumathi and Deepa
Introduction to Simulink(companion application to MATLAB) with Engineering Applications
Intuitive Probability and Random Processes Using MatLab - Steven M. Kay
Kalman Filtering Theory and Practice Using MATLAB - Grewal and Andrews
Learning Matlab 6, Release 12, Student Version
Learning Programming Using MATLAB - Khalid Sayood
MathWorks Documentation - MATLAB V7 Function References
MathWorks Documentation - MATLAB V7 Introductory and Programming
MATLAB Companion for Multivariable Calculus
Matlab Guide
MATLAB Primer, Sixth Edition
MATLAB Primer,Seventh Edition
MATLAB Programming for Engineers
Matlab Programming
MATLAB Recipes for Earth Sciences
MATLAB Simulations for Radar Systems Design
MATLAB(R) for Photomechanics- A Primer
MATLAB.Demystified.Apr.2007
Mechanics of Composite Materials with MATLAB
Numerical Analysis Using MATLAB and Excel - Steven T. Karris
Numerical Analysis Using MATLAB and Spreadsheets - Steven T. Karris
Numerical Computing with MATLAB - Cleve Moler.zip
Numerical Methods in Engineering with MATLAB
Numerical Methods in Finance and Economics A MATLAB-Based Introduction, 2nd Edition
Numerical Methods using MATLAB 3rd Ed - Mathews and Fink
Numerical Techniques for Chemical & Biological Engineers Using MATLAB - Elnashaie & Uhlig
Optical Scanning Holography with MATLAB - Ting Chung Poon
Optics Learning by Computing with Examples using MATLAB - K.D. Moller
Ordinary and Partial Differential Equation Routines in C, C++, Fortran, Java, Maple, and MATLAB - H.J. Lee & W.E. Schiesse
Process Control A First Course with MATLAB
Radar Systems Analysis and Design Using MatLab - Mahafza Bassem R
Robust Control Design with Matlab - Gu Petkov and Konstantinov
Scientific Computing with MATLAB - Alfio Quarteroni and Fausto Saleri
Scientific Computing with MATLAB and Octave
Signals and Systems with MATLAB Applications, Second Edition
Signals and Systems with MATLAB Computing and Simulink Modeling - Steven T. Karris
Simulink Dynamic System Simulation for Matlab User's Guide
Solving ODEs with MATLAB - Shampine Gladwell Thompson
Solving ODEs with Matlab Instructors Manual - L.F. Shampine.zip
Spectral Methods in MATLAB - Lloyd N. Trefethen
Using matlab_6 graphics
Vibration Simulation Using MATLAB and ANSYS - Michael R Hatch

Friday, January 16, 2009

List of Books

Books list :
(1) Vacuum Technology
(2)Hall Effect Devices
(3) Bulk Crystal Growth in Electroni,optical and Optoelectronic and Materials