The American Dream Essays (400 words) - The Great Gatsby

The American Dream In The Great Gatsby, F. Scott Fitzgerald uses many repeated references to time in order to draw attention to the so-called American Dream, which is something Jay Gatsby sorely desires in this novel. Time is the most important motif in The Great Gatsby, the word itself appears 87 times! Gatsby is constantly striving to get back to that perfect moment in time is to recapture Daisy's heart. These time references are expressed through all the literary techniques. Some episodes which symbolize time are when Gatsby knocks over the clock and his list of famous party guests written on a timetable. Time itself is a dissolution, and therefore symbolizes the irony of the American Dream, another dissolution. As time passes, Gatsby and his aspirations for realizing this Dream seem to drift farther and farther apart. Others in the novel are striving for this patriotic goal as well. Myrtle (who's name is a noxious weed vine, that strives to climb) thinks she can find it through love; love of Tom Buchanan's money. The yellow-gold car that killed her (gold representing riches) is really her passion for all things materialistic shattering her dream. George Wilson, probably the most honest character in the book, also thinks the answer to finding the dream is love, but real love; for Myrtle, and himself. When he thinks Gatsby has killed his love, he kills him and then himself, knowing that his version of the dream is unattainable. The two people who truly appear to live the dream are Tom and Daisy. But they cheat on each other and have no love for one another. What kind of dream is that? Jay Gatsby threw extravagant parties in order to see Daisy, who never showed (But, then again neither did he). He peered out of his mansion, a mere copy of grandeur, and watched other dreamers pass their time.And as for time, the novel begins with the phrase: In my younger and more vulnerable years... and ends with ...borne bck ceaselessly into the past. Both emphasize the ignificance of time. The only compliment Nick ever pays tsby shows how the American Dream is not so valid in theGreat Gatsby. As Nick is leaving Gatsby's house, he shoutsfrom the lawn,They're a rotten crowd....you're worth thewhole bunch put together. l in all, time has eroded all these characters' perception of the American Dream. English Essays

What Were the Consequences of the Vietnam War for Civilians essays

What Were the Consequences of the Vietnam War for Civilians essays The US withdrawal made many problems for people on both sides. The Americans suffered mainly from the indignity of loosing and also the consequences of there use of things like Agent Orange.. The Vietnamese people suffered by having the aftermath of the US actions, they suffered famine and the significant problems of having deformed children. The effects of chemical warfare, although people had speculated about long term effects, they only really became apparent after the war. Like the links of Agent Orange with cancer, then in 1985 the first ideas that illness may be passed through generations were considered but were not proved until 1993. The land was badly contaminated by the use of chemicals, Vietnam had gone from one of the major rice producing countries to not being able to grow any thing, not even the relatively small amount to survive on a subsistence level. The Vietnamese people were then forced to import food, this began economic problems as there was no money to help theses people. Especially as inflation was at 700% and the Russians stooped providing the country with aid in 1991 The debree from the war posed a threat to Vietnamese people in unexploded land mines and sharp pieces of metal and so the unsuitability to farm the land or build on it. Other wars broke out in Vietnam with Cambodia and China, numerous people decided to leave. Many of these by boat, as many people as possible would be crammed into small vessels before sailing for Hong Kong or Thailand. Many of these boats were attacked by pirates or sank. Roughly 50,000 of the 'boat people' drowned. About a million were successful in traveling west settling in Britain and in the US. Things began to look up when, in 1993 the Americans allowed the international monetary fund and world bank to start investing in Vietnam. Then the trade embargo was lifted by 1995. Only 20 years after the US withdrawal were full diplomatic relations rees ...

A close textual analysis of Aristotle BOOK 2 chapter 3 Essay

A close textual analysis of Aristotle BOOK 2 chapter 3 - Essay Example The formal cause is â€Å"the account of what the being would be†, its genera and its parts, e.g. number and ration of two to one are causes of an octave. The efficient cause, â€Å"the primary source of the change or staying unchanged†, is â€Å"that which makes something of that which is made† and â€Å"changes something of that which is changed†, e.g. the sculptor, parents, etc. At last the final cause is the end of a thing, i.e. â€Å"what something is for†, e.g. health is the final cause of walking and purging, drugs and surgical instruments (pp.28-29; 194 b 20 – 35). Here it is necessary to dwell upon the nature of causes. Aristotle himself notes that â€Å"many different things are called† and â€Å"can be causes† of the same thing, as well as the same thing can be a cause for many phenomena. First of all, as we try to understand the notion of â€Å"cause† in terms of cause-and-effect position, it becomes wholly unclear how bronze may cause a statue, or whether a table can be caused by wood it is made of. Then as we remember that we read Aristotle in translation from Greek, you realize that the word could perhaps be interpreted by the means of other words. Indeed, the Greek aition has transformed into the present Italian aita (assistant), aiutare (to assist). Thus we understand the cause as something assisting, making another thing. In this case we may say that material assists the emergence of a form, i.e. a form is made out of the material and is impossible without it. The form assists things in fulfilling their functions. It would be difficult to use a shaky table with a vertical top. A carpenter assists the emergence of the table. Due to carpenter’s knowledge and skills of how to make tables this emergence is possible. Finally, it is the functions or purpose of the table which assist in the emergence of this piece of furniture being produced of definite firm materials and of definite form. Such a

Why life insurance is or is not appropriate in Islamic countries Research Paper

Why life insurance is or is not appropriate in Islamic countries - Research Paper Example The first one of the view that insurance of any kind is prohibited because it is an agreement based on doubts, it is against God’s commands and insurance business is based on interest. Life insurance is used to cover financial loss happening from death. It is impossible to define life insurance in a single definition as there are different ways to explain it. In simple words life insurance is a tool to safeguard against natural calamities. The aim of every individual is to secure his family from future risks. Every person dreams for prosperous life for his near and dear ones, a bright future for their children and self without depending on others. The life insurance guarantees materializing these aims by paying them in terms of money. There was a time when necessities of life were fulfilled by government or charity organizations. As the population increases the resources are shrinking day by day. World is being governed by man-made laws and lust for power and corruption is multiplying in every walk of life. Basic necessities like food, shelter, education and social services are no more available. Even fresh and unpolluted breathing is no more. It seems difficult to make both ends meet. Individual earning in a family when meets with any misfortune like natural death, Job termination, disability etc than one can imagine how he will cope with all this. Here life insurance is the only option available to avail in this situation. Life insurance is a vast subject if studied it will give you a short- cut to fulfill above mentioned noble commitments. After collecting large sum of money from the public the insurance company with the government’s assistance can run various projects at national level. Through all this government uses this cash for various schemes such as power generation, special education, employment generation etc. In return government pays suitable interest so that public should get their maximum profit at

Its a Flat World, After All by Thomas Friedman Essay

Its a Flat World, After All by Thomas Friedman - Essay Example Friedman discusses the different flatteners of the world which have created a level playing field for all countries. These flatteners include the collapse of the Berlin Wall, Netscape, Workflow software, uploading, outsourcing, offshoring, supply chaining, insourcing, informing, and steroids. In reviewing these flatteners, it is important to understand the context upon which the word flattened or flat is used. Friedman uses the term flat in terms of the level of competence which all countries have in terms of access to information and technology, including economic growth and development. Such information is used in various activities including business, governance, education, and sports. Based on Friedman’s arguments, he concludes that the world is flat because the access to information, technology, and the potential for economic growth is no longer the exclusive province of the developed states (Bijker, 1995). Instead, the economic, political, and social landscape has levele d out and this process has started unfolding ever since the fall of the Berlin Wall, becoming even more apparent starting in the year 2000 onwards. Undeniably, the use of technology and the spread and the access of information have become very much apparent in the current setting. The information represents an â€Å"assemblage of data† (Headrick, 2000, p. ... The information and technology are no longer exclusive or delayed in transmission. For a long, while geographical barriers between countries implied that different nations had different rates of growth; however, geographical barriers have become less of an issue through internet capability (Suchman, 2007). In relation to internet access therefore, Friedman provides strong support for the world being flat and less hierarchical. Since information is no longer exclusive to specific individuals or countries, the possibility of creating technology and innovations from such information is no longer also an exclusive right and privilege of specific countries (Wolf, 2008). This indicates that there are also innovators which can gain access to the same information from any part of the globe and then transform such information to innovations. For a long while, the US and other western nations were the global leaders in technology and innovation (Beniger, 1986). From such technology and innovat ions, they were able to make major advancements in labor-saving technology which increased productivity and made the work hours more efficient. With â€Å"falling communication costs and the broader spectrum of activities that can be coordinated through current forms of computer-mediated interaction,† more economic links were soon established (Kallinikos, 2010, p. 93). From such technology and innovations, the rest of the world looked to the west for dole-outs of these technologies. The adaptation of these technologies was carried out in order for the countries to keep up with western technologies.  

Sources of noise in transistor

Sources of noise in transistor SOURCE OF NOISE IN TRANSISTOR FOR DIFFERENT CONFIGURATION Abstract- Here in this term paper, I am going to discuss the history of the transistors, its importance and its limitations. The term paper is on the sources of noise in transistors for different configurations. HISTORY A replica of the first working transistor. The first patent for the field-effect transistor principle was filed in Canada by Austrian-Hungarian physicist Julius Edgar Lilienfeld on October 22, 1925, but Lilienfeld did not publish any research articles about his devices. In 1934 German physicist Dr. Oskar Heil patented another field-effect transistor. On 17 November 1947 John Bardeen and Walter Brattain, at ATT Bell Labs, observed that when electrical contacts were applied to a crystal of germanium, the output power was larger than the input. William Shockley saw the potential in this and worked over the next few months greatly expanding the knowledge of semiconductors and is considered by many to be the father of the transistor. The term was coined by John R. Pierce. IMPORTANCE The transistor is considered by many to be the greatest invention of the twentieth-century, or as one of the greatest. It is the key active component in practically all modern electronics. Its importance in todays society rests on its ability to be mass produced using a highly automated process (fabrication) that achieves astonishingly low per-transistor costs. Although several companies each produce over a billion individually-packaged (known as discrete) transistors every year, the vast majority of transistors produced are in integrated circuits (often shortened to IC, microchips or simply chips) along with diodes, resistors, capacitors and other electronic components to produce complete electronic circuits. A logic gate consists of about twenty transistors whereas an advanced microprocessor, as of 2006, can use as many as 1.7 billion transistors (MOSFETs). About 60 million transistors were built this year [2002] for [each] man, woman, and child on Earth. The transistors low cost, flexibility and reliability have made it a ubiquitous device. Transistorized mechatronic circuits have replaced electromechanical devices in controlling appliances and machinery. It is often easier and cheaper to use a standard microcontroller and write a computer program to carry out a control function than to design an equivalent mechanical control function.[1] USAGE The bipolar junction transistor, or BJT, was the first transistor invented, and through the 1970s, was the most commonly used transistor. Even after MOSFETs became available, the BJT remained the transistor of choice for many analog circuits such as simple amplifiers because of their greater linearity and ease of manufacture. Desirable properties of MOSFETs, such as their utility in low-power devices, usually in the CMOS configuration, allowed them to capture nearly all market share for digital circuits; more recently MOSFETs have captured most analog and power applications as well, including modern clocked analog circuits, voltage regulators, amplifiers, power transmitters, motor drivers, etc. BJT used as an electronic switch, in grounded-emitter configuration. How a transistor works Amplifier circuit, standard common-emitter configuration. Simple circuit using a transistor. Operation graph of a transistor The essential usefulness of a transistor comes from its ability to use a small signal applied between one pair of its terminals to control a much larger signal at another pair of terminals. This property is called gain. A transistor can control its output in proportion to the input signal; this is called an amplifier. Or, the transistor can be used to turn current on or off in a circuit like an electrically controlled switch, where the amount of current is determined by other circuit elements. The two types of transistors have slight differences in how they are used in a circuit. A bipolar transistor has terminals labelled base, collector and emitter. A small current at base terminal can control or switch a much larger current between collector and emitter terminals. For a field-effect transistor, the terminals are labelled gate, source, and drain, and a voltage at the gate can control a current between source and drain. The image to the right represents a typical bipolar transistor in a circuit. Charge will flow between emitter and collector terminals depending on the current in the base. Since internally the base and emitter connections behave like a semiconductor diode, a voltage drop develops between base and emitter while the base current exists. The size of this voltage depends on the material the transistor is made from, and is referred to as VBE. Transistors are commonly used as electronic switches, for both high power applications including switched-mode power supplies and low power applications such as logic gates. It can be seen from the graph that once the base voltage reaches a certain level, shown at B, the current will no longer increase with increasing VBE and the output will be held at a fixed voltage.[dubious discuss] The transistor is then said to be saturated. Hence, values of input voltage can be chosen such that the output is either completely off, or completely on. The transistor is acting as a switch, and this type of operation is common in digital circuits where only on and off values are relevant. TRANSISTOR AS AN AMPLIFIER The above common emitter amplifier is designed so that a small change in voltage in (Vin) changes the small current through the base of the transistor and the transistors current amplification combined with the properties of the circuit mean that small swings in Vin produce large changes in Vout. It is important that the operating parameters of the transistor are chosen and the circuit designed such that as far as possible the transistor operates within a linear portion of the graph, such as that shown between A and B, otherwise the output signal will suffer distortion. Various configurations of single transistor amplifier are possible, with some providing current gain, some voltage gain, and some both. From mobile phones to televisions, vast numbers of products include amplifiers for sound reproduction, radio transmission, and signal processing. The first discrete transistor audio amplifiers barely supplied a few hundred milliwatts, but power and audio fidelity gradually increased as better transistors became available and amplifier architecture evolved. Modern transistor audio amplifiers of up to a few hundred watts are common and relatively inexpensive. Some musical instrument amplifier manufacturers mix transistors and vacuum tubes in the same circuit, as some believe tubes have a distinctive sound.Prior to the development of transistors, vacuum (electron) tubes (or in the UK thermionic valves or just valves) were the main active components in electronic equipment. ADVANTAGES The key advantages that have allowed transistors to replace their vacuum tube predecessors in most applications are: I. Small size and minimal weight, allowing the development of miniaturized electronic devices. II. Highly automated manufacturing processes, resulting in low per-unit cost. III. Lower possible operating voltages, making transistors suitable for small, battery-powered applications. IV. No warm-up period for cathode heaters required after power application. V. Lower power dissipation and generally greater energy efficiency. VI. Higher reliability and greater physical ruggedness. VII. Extremely long life. Some transistorized devices produced more than 30 years ago are still in service. VIII. Complementary devices available, facilitating the design of complementary-symmetry circuits, something not possible with vacuum tubes. IX. Insensitivity to mechanical shock and vibration, thus avoiding the problem of microphonics in audio applications. [2] LIMITATIONS I. Silicon transistors do not operate at voltages higher than about 1,000 volts (SiC devices can be operated as high as 3,000 volts). In contrast, electron tubes have been developed that can be operated at tens of thousands of volts. II. High power, high frequency operation, such as used in over-the-air television broadcasting, is better achieved in electron tubes due to improved electron mobility in a vacuum. III. On average, a higher degree of amplification linearity can be achieved in electron tubes as compared to equivalent solid state devices, a characteristic that may be important in high fidelity audio reproduction. IV. Silicon transistors are much more sensitive than electron tubes to an electromagnetic pulse, such as generated by a nuclear explosion. V. Semiconductor material: germanium, silicon, gallium arsenide, silicon carbide, etc. VI. Structure: BJT, JFET, IGFET (MOSFET), IGBT, other types VII. Polarity: NPN, PNP (BJTs); N-channel, P-channel (FETs) VIII. Maximum power rating: low, medium, high IX. Maximum operating frequency: low, medium, high, radio frequency (RF), microwave (The maximum effective frequency of a transistor is denoted by the term fT, an abbreviation for frequency of transition. The frequency of transition is the frequency at which the transistor yields unity gain). X. Application: switch, general purpose, audio, high voltage, super-beta, matched pair XI. Physical packaging: through hole metal, through hole plastic, surface mount, ball grid array, power modules XII. Amplification factor hfe (transistor beta) Thus, a particular transistor may be described as: silicon, surface mount, BJT, NPN, low power, high frequency switch. The bipolar junction transistor (BJT) was the first type of transistor to be mass-produced. Bipolar transistors are so named because they conduct by using both majority and minority carriers. The three terminals of the BJT are named emitter, base and collector. Two p-n junctions exist inside a BJT: the base/emitter junction and base/collector junction. The [BJT] is useful in amplifiers because the currents at the emitter and collector are controllable by the relatively small base current. In an NPN transistor operating in the active region, the emitter-base junction is forward biased, and electrons are injected into the base region. Because the base is narrow, most of these electrons will diffuse into the reverse-biased base-collector junction and be swept into the collector; perhaps one-hundredth of the electrons will recombine in the base, which is the dominant mechanism in the base current. By controlling the number of electrons that can leave the base, the number of electrons ent ering the collector can be controlled. Unlike the FET, the BJT is a low-input-impedance device. Also, as the base-emitter voltage (Vbe) is increased the base-emitter current and hence the collector-emitter current (Ice) increase exponentially according to the Shockley diode model and the Ebers-Moll model. Because of this exponential relationship, the BJT has a higher transconductance than the FET. Bipolar transistors can be made to conduct by exposure to light, since absorption of photons in the base region generates a photocurrent that acts as a base current; the collector current is approximately beta times the photocurrent. Devices designed for this purpose have a transparent window in the package and are called phototransistors. FIELD EFFECT TRANSISTORS The field-effect transistor (FET), sometimes called a unipolar transistor, uses either electrons (in N-channel FET) or holes (in P-channel FET) for conduction. The four terminals of the FET are named source, gate, drain, and body (substrate). On most FETs, the body is connected to the source inside the package, and this will be assumed for the following description. In FETs, the drain-to-source current flows via a conducting channel that connects the source region to the drain region. The conductivity is varied by the electric field that is produced when a voltage is applied between the gate and source terminals; hence the current flowing between the drain and source is controlled by the voltage applied between the gate and source. As the gate-source voltage (Vgs) is increased, the drain-source current (Ids) increases exponentially for Vgs below threshold, and then at a roughly quadratic rate (I_{ds} propto (V_{gs}-V_T)^2) (where VT is the threshold voltage at which drain current begins) in the space-charge-limited region above threshold. A quadratic behavior is not observed in modern devices, for example, at the 65 nm technology node. For low noise at narrow bandwidth the higher input resistance of the FET is advantageous. FETs are divided into two families: junction FET (JFET) and insulated gate FET (IGFET). The IGFET is more commonly known as metal-oxide-semiconductor FET (MOSFET), from their original construction as a layer of metal (the gate), a layer of oxide (the insulation), and a layer of semiconductor. Unlike IGFETs, the JFET gate forms a PN diode with the channel which lies between the source and drain. Functionally, this makes the N-channel JFET the solid state equivalent of the vacuum tube triode which, similarly, forms a diode between its grid and cathode. Also, both devices operate in the depletion mode, they both have a high input impedance, and they both conduct current under the control of an input voltage. Metal-semiconductor FETs (MESFETs) are JFETs in which the reverse biased PN junction is replaced by a metal-semiconductor Schottky-junction. These, and the HEMTs (high electron mobility transistors, or HFETs), in which a two-dimensional electron gas with very high carrier mobility is used for charge transport, are especially suitable for use at very high frequencies (microwave frequencies; several GHz). Unlike bipolar transistors, FETs do not inherently amplify a photocurrent. Nevertheless, there are ways to use them, especially JFETs, as light-sensitive devices, by exploiting the photocurrents in channel-gate or channel-body junctions. FETs are further divided into depletion-mode and enhancement-mode types, depending on whether the channel is turned on or off with zero gate-to-source voltage. For enhancement mode, the channel is off at zero bias, and a gate potential can enhance the conduction. For depletion mode, the channel is on at zero bias, and a gate potential (of the opposite polarity) can deplete the channel, reducing conduction. For either mode, a more positive gate voltage corresponds to a higher current for N-channel devices and a lower current for P-channel devices. Nearly all JFETs are depletion-mode as the diode junctions would forward bias and conduct if they were enhancement mode devices; most IGFETs are enhancement-mode types.[3] OTHER TRANSISTORS TYPE I. Point-contact transistor, first type of transistor ever constructed II. Bipolar junction transistor (BJT) a. Heterojunction bipolar transistor up to 100s GHz, common in modern ultrafast and RF circuits b. Grown-junction transistor, first type of BJT c. Alloy-junction transistor, improvement of grown-junction transistor i. Micro-alloy transistor (MAT), faster than alloy-junction transistor ii. Micro-alloy diffused transistor (MADT), faster than MAT, type of a diffused-base transistor iii. Post-alloy diffused transistor (PADT), faster than MAT, type of a diffused-base transistor iv. Schottky transistor v. Surface barrier transistor d. Drift-field transistor e. Avalanche transistor f. Darlington transistors are two BJTs connected together to provide a high current gain equal to the product of the current gains of the two transistors. g. Insulated gate bipolar transistors (IGBTs) use a medium power IGFET, similarly connected to a power BJT, to give a high input impedance. Power diodes are often connected between certain terminals depending on specific use. IGBTs are particularly suitable for heavy-duty industrial applications. The Asea Brown Boveri (ABB) 5SNA2400E170100 illustrates just how far power semiconductor technology has advanced. Intended for three-phase power supplies, this device houses three NPN IGBTs in a case measuring 38 by 140 by 190mm and weighing 1.5kg. Each IGBT is rated at 1,700 volts and can handle 2,400 amperes. h. Photo transistor React to light III. Field-effect transistor a. JFET, where the gate is insulated by a reverse-biased PN junction b. MESFET, similar to JFET with a Schottky junction instead of PN one i. High Electron Mobility Transistor (HEMT, HFET, MODFET) c. MOSFET, where the gate is insulated by a thin layer of insulator d. Inverted-T field effect transistor (ITFET) e. FinFET The source/drain region forms fins on the silicon surface. f. FREDFET Fast-Reverse Epitaxial Diode Field-Effect Transistor g. Thin film transistor Used in LCD display. h. OFET Organic Field-Effect Transistor, in which the semiconductor is an organic compound i. Ballistic transistor j. Floating-gate transistor Used for non-volatile storage. k. FETs used to sense environment i. Ion sensitive field effect transistor To measure ion concentrations in solution. ii. EOSFET Electrolyte-Oxide-Semiconductor Field Effect Transistor (Neurochip) iii. DNAFET Deoxyribonucleic acid field-effect transistor IV. Spacistor V. Diffusion transistor, formed by diffusing dopants into semiconductor substrate; can be both BJT and FET VI. Unijunction transistors can be used as simple pulse generators. They comprise a main body of either P-type or N-type semiconductor with ohmic contacts at each end (terminals Base1 and Base2). A junction with the opposite semiconductor type is formed at a point along the length of the body for the third terminal (Emitter). VII. Single-electron transistors (SET) consist of a gate island between two tunnelling junctions. The tunnelling current is controlled by a voltage applied to the gate through a capacitor. VIII. Spin transistor Magnetically-sensitive IX. Nanofluidic transistor Control the movement of ions through sub-microscopic, water-filled channels. Nanofluidic transistor, the basis of future chemical processors X. Multigate devices a. Tetrode transistor b. Pentode transistor c. Multigate device d. Trigate transistors (Prototype by Intel) e. Dual gate FETs have a single channel with two gates in cascode; a configuration that is optimized for high frequency amplifiers, mixers, and oscillators f. Semiconductor material XI. The first BJTs were made from germanium (Ge). Silicon (Si) types currently predominate but certain advanced microwave and high performance versions now employ the compound semiconductor material gallium arsenide (GaAs) and the semiconductor alloy silicon germanium (SiGe). Single element semiconductor material (Ge and Si) is described as elemental. Rough parameters for the most common semiconductor materials used to make transistors are given in the table below; it must be noted that these parameters will vary with increase in temperature, electric field, impurity level, strain and various other factors: Semiconductor material characteristics Semiconductormaterial Junction forwardvoltageV @ 25  °C Electron mobilitym ²/(V ·s) @ 25  °C Hole mobilitym ²/(V ·s) @ 25  °C Max. junction temp. °C Ge 0.27 0.39 0.19 70 to 100 Si 0.71 0.14 0.05 150 to 200 GaAs 1.03 0.85 0.05 150 to 200 Al-Si junction 0.3 — — 150 to 200 The junction forward voltage is the voltage applied to the emitter-base junction of a BJT in order to make the base conduct a specified current. The current increases exponentially as the junction forward voltage is increased. The values given in the table are typical for a current of 1 mA (the same values apply to semiconductor diodes). The lower the junction forward voltage the better, as this means that less power is required to drive the transistor. The junction forward voltage for a given current decreases with increase in temperature. For a typical silicon junction the change is approximately −2.1 mV/ °C. The density of mobile carriers in the channel of a MOSFET is a function of the electric field forming the channel and of various other phenomena such as the impurity level in the channel. Some impurities, called dopants, are introduced deliberately in making a MOSFET, to control the MOSFET electrical behavior. The electron mobility and hole mobility columns show the average speed that electrons and holes diffuse through the semiconductor material with an electric field of 1 volt per meter applied across the material. In general, the higher the electron mobility the faster the transistor. The table indicates that Ge is a better material than Si in this respect. However, Ge has four major shortcomings compared to silicon and gallium arsenide: I. its maximum temperature is limited II. it has relatively high leakage current III. it cannot withstand high voltages IV. it is less suitable for fabricating integrated circuits Because the electron mobility is higher than the hole mobility for all semiconductor materials, a given bipolar NPN transistor tends to be faster than an equivalent PNP transistor type. GaAs has the highest electron mobility of the three semiconductors. It is for this reason that GaAs is used in high frequency applications. A relatively recent FET development, the high electron mobility transistor (HEMT), has a heterostructure (junction between different semiconductor materials) of aluminium gallium arsenide (AlGaAs)-gallium arsenide (GaAs) which has double the electron mobility of a GaAs-metal barrier junction. Because of their high speed and low noise, HEMTs are used in satellite receivers working at frequencies around 12GHz. Max. junction temperature values represent a cross section taken from various manufacturers data sheets. This temperature should not be exceeded or the transistor may be damaged. Al-Si junction refers to the high-speed (aluminum-silicon) semiconductor-metal barrier diode, commonly known as a Schottky diode. This is included in the table because some silicon power IGFETs have a parasitic reverse Schottky diode formed between the source and drain as part of the fabrication process. This diode can be a nuisance, but sometimes it is used in the circuit.[4] Packaging Through-hole transistors (tape measure marked in centimetres) Transistors come in many different packages (chip carriers) (see images). The two main categories are through-hole (or leaded), and surface-mount, also known as surface mount device (SMD). The ball grid array (BGA) is the latest surface mount package (currently only for large transistor arrays). It has solder balls on the underside in place of leads. Because they are smaller and have shorter interconnections, SMDs have better high frequency characteristics but lower power rating. Transistor packages are made of glass, metal, ceramic or plastic. The package often dictates the power rating and frequency characteristics. Power transistors have large packages that can be clamped to heat sinks for enhanced cooling. Additionally, most power transistors have the collector or drain physically connected to the metal can/metal plate. At the other extreme, some surface-mount microwave transistors are as small as grains of sand. Often a given transistor type is available in different packages. Transistor packages are mainly standardized, but the assignment of a transistors functions to the terminals is not: different transistor types can assign different functions to the packages terminals. Even for the same transistor type the terminal assignment can vary (normally indicated by a suffix letter to the part number- i.e. BC212L and BC212K)[5]. CONCLUSION A unified noise model which incorporates both the number fluctuation and the correlated surface mobility fluctuation mechanism is discussed. The latter is attributed to the Coulombic scattering effect of the fluctuating oxide charge. The model has a functional form resembling that of the number fluctuation theory, but at certain bias conditions it may reduce to a form compatible with Hooges empirical expression. The model can unify the noise data reported in the literature, without making any ad hoc assumption on the noise generation mechanism. Specifically, the model can predict the right magnitude and bias dependence of the empirical Hooge parameter. Simulated noise characteristics obtained with a circuit-simulation-oriented fnoise model based on the new formulation were compared with experimental noise data. Excellent agreement between the calculations and measurement was observed in both the linear and saturation regions for MOS transistors fabricated by different technologies. T he work shows that the flicker noise in MOS transistors can be completely explained by the trap charge fluctuation mechanism, which produces mobile carrier number fluctuation and correlated surface mobility fluctuationIn electronics, a transistor is a semiconductor device commonly used to amplify or switch electronic signals. A transistor is made of a solid piece of a semiconductor material, with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistors terminals changes the current flowing through another pair of terminals. Because the controlled (output) power can be much larger than the controlling (input) power, the transistor provides amplification of a signal. The transistor is the fundamental building block of modern electronic devices, and is used in radio, telephone, computer and other electronic systems. Some transistors are packaged individually but most are found in integrated circuits. REFERENCES- [1]www.ciphersbyritter.com/NOISE/NOISRC.HTM [2]www.nikhef.nl/~jds/vlsi/noise/transistor [3]www.colorado.edu/physics/phys3330/phys3330_fa05/manual/Exp [4]www.imagesensors.org/Past%20Workshops/2003%20Workshop/2003%20Papers/27%20Findlater%20et%20al [5]www.ansoft.com/news/articles/HF0605

The importance of the role played by the educated elite in the process

africa came under the direct jurisdiction of Europe after the initial carving out of the continent referred to as the 'Scramble for Africa'. This partition was fulfilled at the Conference of Berlin 1884-85 resulting in the political mapping of the continent. Thus, Africa facilitated the extension of the European hegemonic powers overseas. This colonization rendered the African continent the play-toy of wealthy European imperialists who raked the profits from the resource-rich territories. The period between 1880 and 1919 saw an upsurge of African resistance to colonial rule this was the period of African nationalism. The Africans were now exasperated with their economic and social situation. Thus discontent and protest was bound to surface. During colonialism generally there was the raising of a small group usually through education and a diffusion of European culture. For the French and the British the style of education was different, the French was one of making French men in Afr ica while the British was more indirect. However it was this group that benefited from education whether French or British were to play a key role in the decolonisation process. Crowder states that the First World War raised the hopes of this emergent class all over Africa that they would be given positions of significance and respect from the colonizers; however these hopes were never realised. The traditional elites were also disgruntled with colonisation as many of them lost their positions and respect not only from the colonizers but also from their people. Moreover, where they retained their positions many of them became puppets of the colonisers. The loss of real power, respect and social standing became a source of discontent among many of them. Neither set of elites were satisfied with colonial rule. An international congress which was convened under the auspices of the comintern at Brussels on February 1927 resulted in the formation of the league against imperialism and for national independence; this provided further impetus for the decolonisation schemes. The congress was attended by 180 delegates from Western Europe, north central and South America, the Caribbean, Asia and Africa. The congress brought together socialists like the independent labour party, the radical leaders in colonial territories and representatives from Africa including Messali Hadj, Abd al-Kadir f... ... In some parts of Africa, European control ended by the early 1970's however a visible and dramatic legacy of colonial rule remained in the form of white colonial elites. due to the apartheid restrictions attempts were made to form political organizations there was the south African native national congress under the leadership of Clements Kadalie, there was also the industrial and commercial workers union whose membership grew to two hundred thousand despite the whites despite attempt to hold on to power. And although they did not receive full sovereignty until later the significance of the political groups played a significant role. Thus, in the former British colonies of Rhodesia (Zimbabwe) and South Africa, the small white minority held onto power over the disenfranchised and repressed black African populations well into the 1980's. It was only with the ending of white rule in Rhodesia in 1980, and the final crumbling of the racist policies of apartheid in S. Africa in 1990 t hat decolonization finally reached all parts of this continent. Nevertheless although their struggle was long it was still through the educated elite with mass support that final independence was achieved.