The Boy Without Penis free essay sample

In 1966, a botched electrical  circumcision left David Reimer (then named Bruce) without a penis. A malfunction in the doctor’s equipment (electro-cautery needle) caused the needle to burn Reimer’s penis from tip to base. The Reimer’s were left with a dilemma: a son with no penis. They visited several medical experts who assured them that penile reconstruction would prove worthless. The Reimer’s were devastated and did not know how to help David. One afternoon when the Reimer’s saw Dr. John Money, a so-called expert in sex reassignment, on television they contacted him and brought their son to see him. It would prove to be a tragic decision. Money persuaded the Reimer’s to reassign their son  as a  female by having his testes removed and naming him Brenda. Dr. Money assured the initially reluctant parents that after the operation was complete raising him as a girl would be successful and no one would be any the wiser. The Reimer’s trusting in the doctor agreed so their child may have a normal life. Money  met with  Ã¢â‚¬ Brenda† once a year throughout the following years to report on her progress. In spite of growing evidence that Brenda was not adjusting well to her gender reassignment, Money published papers to the contrary. In psychiatric circles to protect Reimer’s identity  Money referred to â€Å"Brenda† as John/Joan. Money’s experiment became well-known in psychiatric communities worldwide and partly as a result of Money’s publications,  a number of infants   born with ambiguous genitalia  underwent gender reassignment. However many psychologists were unconvinced about the John/Joan experiment. One of these was academic sexologist Milton Diamond, who, in a bold move against Money reported to the psychiatric community that Reimer never identified as female, and that he began living as a male from the age of 15. Sexual reassignment in the Reimer case is not a gender identity disorder. He was born male  unlike than intersex  (hermaphrodite) individuals. Intersex is a term that usually defines  discordance of the biological aspects of sexual gender. Traits related to the genitalia, such as internal organs, gonadal tissue, or chromosomes that are more typical of the other sex, or incompletely differentiated  define the intersex individual. Sub-types of hermaphroditism include: 1. Pseudohermaphroditism Typically a female   has a clitoris that is greatly enlarged to the point that they  are categorized as intersexed. These people are identified immediately at birth as intersex  because those with the condition have a sexual organ larger than a clitoris and smaller than a penis 2. Simultaneous hermaphrodite (intersex)  A simultaneous   hermaphrodite (homogamy) is a person that has both male and female sexual organs. This definition tends to be misleading since there have been very few human beings with fully developed male and female internal and external genitalia and female breasts. Normally one genitalia is more prominent than the other. Some people who are intersex individuals, such as those with Klinefelter’s syndrome and androgen insensitivity syndrome, appear completely female or male without realizing they are intersexed. An intersex person may express diversion from typical XX-female or XY-male chromosomes, for example a sex reversal of XY-female and XX-male. Sometimes an intersex person who is born with partially formed dual genitalia prefers one gender over the other. Sometimes they don’t. Their commonality with David Reimer is that the assignment of their gender should be their own choice rather than that of the medical community. One of the most difficult  experiences Reimer faced due to his increasingly  unusual looks and behaviours  was rejection from his peers. He became a pariah during his elementary school years. From as early as kindergarten, he was a target for bullying by both male and female. â€Å"As [I’d ]walk by, they’d start giggling. Not one, but almost the whole class. It’d be like that every day. The whole school would make fun of  [me] about one thing or another. † In his early teens  Reimer attended a technical high school. Right away his peers dubbed him  Cave-woman and told him, â€Å"You’re a boy. † But it was his habit of urinating standing up that caused the greatest  problem between  Reimer and  his schoolmates. The girls  prevented him from using their bathroom. When he tried to use the boys’ room  he was threatened with a knife. By December, he dropped out of school. with struggling against emotional uncertainty about his life and his innate attraction to females, Reimer made no friends and  was  forcibly a  loner. During puberty Reimer’s erroneous belief that he was a lesbian added to his emotional angst. The David Reimer case  also serves to  reinforce the  scientific  hypothesis  that sexual orientation is not one of choice. Sexual  orientation is innate, not solely a result of environmental influences although the latter may have some bearing. Watch video Science amp; Homosexuality: Nature vs Nurture No single cause for sexual orientation is conclusively proven. Researchers suggest that a combination of genetic, hormonal, and environmental influences, along with biological factors, genetics and the early uterine environment bear significant influence on sexual orientation. I tend to favour the physio-neurological theory myself. I didn’t choose to be straight. I just am. Watch video Gay Twins and the Science of Epigenetics. We both wanted to play with guys, build forts and have snowball fights and play army. † Reimer finally reached a point where he told his parents if he had to visit his psychologist Dr. Money anymore he would kill himself. It was then that his parents chose to tell him the truth about his gender. Surprisingly, Reimer took the news well. It answered a lot of difficult questions and he began to live his life as a male. He did not use his birth name of Bruce. He chose David. Throughout his teens Reimer seemed well-adjusted and was much happier than he’d been as Brenda. Eventually Reimer met a woman named Jane Fontaine, a single mother. They married and Reimer became both a husband and father. It was during this  well-adjusted time in his life that  Reimer discovered Dr. Money was still claiming that  Reimer’s sex reassignment was highly successful. Money   encouraged the medical and psychiatric communities to conduct the same procedures on children with genital deformities or ambiguous genitalia. Most likely it was due to two factors that Reimer chose to  go public with his personal experience in an effort to contradict Money’s publications: he was  secure within  his marriage to  a supportive spouse and he was determined to expose Money as a fraud. Reimer took part in public television and magazine interviews. When released to the public Reimer’s story loosed an unexpected reaction. Intersex people  born and reassigned after the publication of Money’s false protocols came forward with their stories. Among them was a  San Francisco activist named Cheryl Chase/Brian Sullivan. When she was born Chase displayed ambiguous genitalia with a phallic structure of a size that, if she was female, could be an enlarged clitoris or if she was male, a micropenis. Her doctors assigned Chase as a boy and her parents named her Charlie. But 18 months  later, her parents consulted another team of experts. Based partly on the fact that Chase had a fairly normal vagina, this team of doctors reassigned her as a girl. They amputated her phallus and her parents named her Cheryl. After the operation Cheryl refused to speak for 6 months. In 1995 Chase changed her name again to Bonnie Sullivan. In her mid-30? s Cheryl experienced a mental breakdown due to the reassignment of her gender. Chase advocates a complex  perspective of intersexuality, namely that gender difficulties cannot be eliminated by early genital surgery. ears after Reimer’s public appearances, John Colapinto conducted a telephone  interview with  John Money, who refused to meet in person. His response to Calopinto`s  observation that scientists and psychologists have disproven his book Man amp; Woman, Boy amp; Girl wherein he discussed the John-Joan experiment was,  Ã‚  Ã¢â‚¬Å"It’s part of the antifeminist movement. They say masculinity and femininity are built into the genes, so women should get back to the mattress and the kitchen. †Ã‚  Money stood by his original  summary of the Reimer case and dismissed  Colapinto’s suggestion that he  Ã¢â‚¬Å"misperceived†Ã‚  Reimer’s psychological condition. Colapinto reiterated that significant scientific evidence leaned towards the hypothesis that gender assignment was not as simple as reassigning gender, and asked Money if he was considering making some alternations to  Man  amp; Woman, Boy  amp; Girl to which Money  replied flatly, â€Å"I’ll be dead by then. Suitably, an ambiguous answer from a man  who  spent  most of his career misleading parents and children about ambiguous genitalia. As with many family traumas Reimer’s sex reassignment deeply effected his whole family. â€Å"My parents feel very guilty, as if the whole thing was their fault,†Ã‚  Reimer told Colapinto. â€Å"But i t wasn’t like that. They did what they did out of kindness, and love and desperation. When you’re desperate, you don’t necessarily do all the right things. † Reimer could not possibly have forseen the effect his public appearances would have on his brother Brian. Unable to accept Reimer’s  openly candid  description of his life, and still unable to accept that what was once his sister was now his  brother, Brian  committed suicide by drug overdose. fter Brian’s  suicide Reimer experienced a series of unfortunate developments:his marriage disintegrated; he found himself unable to maintain stable employment; he experienced financial difficulty after making a poor investment;  his anger at Dr. Money and the medical doctor responsible for his gender reassignment intensified;  and his depression returned to haunt him. In May 2004 at the age of 38 Reimer committed suicide with a shotgun.

Speech on Dr. B.R. Ambedkar free essay sample

Ambedkar was born in the British-founded town and military cantonment of Mhow in the Central Provinces (now in Madhya Pradesh). He was the 14th and last child of Ramji Maloji Sakpal and Bhimabai. His family was of Marathi background from the town of Ambavade in the Ratnagiri district of modern-day Maharashtra. They belonged to the Hindu, Mahar caste, who were treated as untouchables and subjected to intense socio-economic discrimination. Belonging to the Kabir Panth, Ramji Sakpal encouraged his children to read the Hindu classics. He used his position in the army to lobby for his children to study at the government school, as they faced resistance owing to their caste. Although able to attend school, Ambedkar and other untouchable children were segregated and given no attention or assistance by the teachers. Ramji Sakpal retired in 1894 and the family moved to  Satara  two years later. Shortly after their move, Ambedkars mother died. We will write a custom essay sample on Speech on Dr. B.R. Ambedkar or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page Of his brothers and sisters, only Ambedkar succeeded in passing his examinations and graduating to a higher school. Ambedkar remarried in 1898, and the family moved to Mumbai (then Bombay), where Ambedkar became the first untouchable student at the Government High School near Elphinstone Road. [7. In 1907, he passed his matriculation examination and entered the University of Bombay, becoming one of the first persons of untouchable origin to enter a college in India. This success provoked celebrations in his community, and after a public ceremony he was presented with a biography of the Buddha by his teacher Krishnaji Arjun Keluskar also known as Dada Keluskar, a Maratha caste scholar. Ambedkars marriage had been arranged the previous year as per Hindu custom, to Ramabai, a nine-year old girl from Dapoli. [7] In 1908, he entered Elphinstone College and obtained a scholarship of twenty five rupees a month from the Gayakwad ruler of Baroda, Sahyaji Rao III. By 1912, he obtained his degree in economics and political science from Bombay University, and prepared to take up employment with the Baroda state government. His wife gave birth to his first son, Yashwant, in the same year. Ambedkar had just moved his young family and started work, when he dashed back to Mumbai to see his ailing father, who died on February 2, 1913. In 1922 through unremitting hard work, Ambedkar once again overfulfilled all expectations:. While practicing law in the Bombay High Court he ran head long in to uplift the untouchable to educate them. . By 1927 Ambedkar decided to launch active movements against untouchability. Upon Indias independence on August 15, 1947, the new Congress-led government invited Ambedkar to serve as the nations first law minister, which he accepted. On August 29, Ambedkar was appointed Chairman of the Constitution Drafting Committee, charged by the Assembly to write free Indias new Constitution. Ambedkar won great praise from his colleagues and contemporary observers for his drafting work. Ambedkar studied Buddhism all his life, and around 1950s, he planned to make a formal conversion back to Buddhism and this work was done by a priest named Chintamani. He was bed-ridden owing to clinical depression and failing eyesight. [11]  . His health worsened as he furiously worked through 1955. Just three days after completing his final manuscript  The Buddha and His Dhamma, it is said that Ambedkar died in his sleep on December 6, 1956 at his home in Delhi. On the anniversary of his birth (14 April) and death (6 December) and on Dhamma Chakra Pravartan Din, 14th Oct at Nagpur, at least half a million people gather to pay homage to him at his memorial in Mumbai. Thousands of bookshops are set up, and books are sold. His message to his followers was Educate!!! , Agitate!!! , Organize!!! .

Lake Essays - Flavored Fortified Wines, Fortified Wine, Pejoratives

ts. They drink ?gin and grape juice, Tango, Thunderbird, and Bali Hai, [sniff] glue, and ether and what somebody [claims] [is] cocaine.?(112) What starts out as a harmless prank on the third night of their summer vacation turns into a situation where they get into a fight, attempt to rape a girl, find a dead body and see first hand the destruction a bad character can do to an automobile. The night they lose their ?badness? is nothing special. After the requisite bad character activities: egging mailboxes and hitchhikers, driving up and down Main Street, eating, drinking, and smoking pot. They decide to go up to the local hangout, *u*Greasy Lake*/u*, to see if anything is going on. They cruise up to the lake with their ?lemon-flavored gin,? requisite pot and the itch for some action. There is no better place, for these three bad characters to hang out - *u*Greasy Lake*/u*, is an important place for bad characters to learn an important lesson. The lake, like the events about to unfold, is ?fetid and murky?mud banks glistened with broken glass [,] strewn with beer cans and the charred remains of bonfires.? (112) There are only two vehicles in the whole parking lot, ?the exoskeleton of some gaunt chrome insect, a chopper leaned against its kickstand.? (113) And a, ?57 Chevy, mint, metallic blue.? (113) No excitement, ?expect some junkie halfwit biker and a car freak pumping his girlfriend.? Whatever they are looking for they are not going to find it up at the lake. All of a sudden, they see a friend?s car. This is all the three need to know; now things will get interesting, maybe it is not a wasted trip after all. They flash the headlights and honk the horn, a harmless prank to pull on a friend, ?for all we [know] we might even catch a glimpse of some little fox?s tit. And then we [could] slap backs with red-faced Tony, roughhouse a little, and go on to new heights of adventure and daring.? (113) In their haste for a little excitement and adventure, they fail to re alize it is not Tony?s car after all, but someone else?s car. This is the second mistake. The first is dropping the car keys in the grass. The owner of the car, a greasy booted character, does not find this childish prank funny. He comes out of the car, with fists flying, feet kicking. He is not about to let these guys get away with this so-called harmless prank. This guy is bad; he takes on all three of the friends, and thoroughly beats them up. Even after this, they still think they are bad. ?[He] [goes] for the tire iron under the car seat.? (114) The narrator still holds onto the idea he is bad, ?[He] [keeps] it there because bad characters always keep tire irons under the driver?s seat, for just such an occasion as this.? (114) Everything the narrator thinks is associated with the image of being bad. The reality is this guy has used the tire iron, not for other fights, but to change a flat tire. As for fighting, this bad character has been in only one other fight in his life ?i n the 6th grade, when a kid with a sleepy eye and two streams of mucous [descending] from his nostrils hit me in the knee with a Louisville slugger.? (114) The situation is taking on a life of it's own, a situation the narrator cannot stop.?[The] antagonist [is] shirtless? he [bends] forward to peel Jeff from his back like a wet over coat?Mother*censored*er, he [spits] over and over, and [the narrator] is aware in that instant that all four [of them] ? Digby, Jeff and [the narrator] included ? [are] chanting mother*censored*er, mother*censored*er as if it were a battle cry.? (114) The adrenaline is pumping, hearts racing; the smell of fear is in the air. They are actors in a play watching from the stage, they are bad. In the heat of the moment; ?[I] [go] at him like a kamikaze, mindless, raging, stung with humiliation ? the whole thing, from the initial boot in the shin to this murderous primal instinct.?

Cunto es posible sacar la green card sin patrocinador

Cunto es posible sacar la green card sin patrocinador    Esto es una excepcià ³n ya que, en general, para conseguir visas de trabajo o la green card se necesita que un ciudadano americano, un residente permanente legal o una empresa americana patrocinen a un extranjero. Pero hay algunas excepciones como la de la EB-5 para inversionistas o, menos conocido pero ampliamente utilizado, del la EB-2 NIW. Quà © es la EB-2 NIW Es un camino hacia la green card sin patrocinador. En otras palabras, los interesados pueden aplicar por sà ­ mismos y no necesitan ni tener un familiar en Estados Unidos ni una oferta de trabajo. NIW significa National Interest Waiver, es decir, esta es una visa EB-2 con ciertas particularidades y en la que se conceden determinados privilegios por razà ³n del interà ©s nacional. Quà © profesionales o empresarios pueden aplicar para la green card sin patrocinador Las personas con estudios de postgraduado, como maestrà ­as o doctorados. O que sean licenciados y puedan demostrar experiencia laboral en su campo de especializacià ³n por un mà ­nimo de cinco aà ±os. Es importantà ­simo que los estudios sean necesarios para desempeà ±ar su ocupacià ³n. Por ejemplo: profesores de escuelas de primaria o secundaria o de universidad, mà ©dicos, cirujanos, abogados, ingenieros, arquitectos, etc. Los extranjeros que puedan demostrar que son profesionales excepcionales, superiores a la media en las Ciencias o en las Artes.Los empresarios excepcionales. En los dos à ºltimos casos el Servicio de Inmigracià ³n y Ciudadanà ­a  (USCIS, por sus siglas en inglà ©s) pide que se cumpla adems con tres de los requisitos siguientes: Diploma o certificado de una universidad o de una institucià ³n relativos con el campo en el que son excepcionales.Las titulaciones extranjeras debern homologarse. Cartas en las que se documente experiencia laboral por un mà ­nimo de diez aà ±os en el rea de especializacià ³n.Membresà ­a en asociaciones profesionales.Licencia para trabajar en esa profesià ³n.Prueba de los salarios recibidos, incluyendo pagos en especie. Deben mostrar el carcter excepcional de la labor realizada. Reconocimiento por parte de colegas, instituciones pà ºblicas, empresariales o profesionales de los logros profesionales o de aportaciones al campo de especializacià ³n.Se admitir cualquier otra prueba semejante que sirva de evidencia de la excepcionalidad profesional. Quà © es el interà ©s nacional en el contexto de la EB-2 NIW Debe entender como de interà ©s nacional las actividades que benefician a la economà ­a de Estados Unidos o a sus intereses culturales o educativos, o al bienestar general del paà ­s. El USCIS debe juzgar que efectivamente las aportaciones laborales que puede hacer el extranjero son substancialmente mayores que las que podrà ­a ofrecer un trabajador americano con las calificaciones mà ­nimas para desempeà ±ar ese trabajo. En el caso de los empresarios, el USCIS ha aclarado que la creacià ³n de empleo y el crecimiento econà ³mico – directo o indirecto- podrà ­an llegar a calificarse como que cumple la exigencia de interà ©s nacional. Quà © pasa si no se cumple con el requisito de interà ©s nacional No podrn auto patrocinarse para una green card. Sin embargo todavà ­a ser posible conseguir una siempre que: Se tenga una oferta de trabajo en la mano. Para conseguirlo hay que buscar trabajo (en inglà ©s)Una empresa o institucià ³n americana està © dispuesta a patrocinar una EB-2 simple. Es la parte patrocinadora quien debe empezar todo el trmite con la forma I-140.Se obtenga una certificacià ³n del Departamento de Trabajo, la forma a rellenar para obtenerla es la ETA-750. Familiares de personas que aplican por una EB-2 NIW La mujer o el marido y los hijos menores de 18 aà ±os podrn obtener una green card (visas E-21 y E-22). Trmites para conseguir la EB-2 NIW Solicitante en Estados Unidos Presentar ante la oficina del USCIS que corresponda la forma I-140 para que apruebe la peticià ³n de la green card y, al mismo tiempo, enviar debidamente cumplimentado el formulario I-485 para el ajuste de estatus. En la actualidad, la resolucià ³n sobre la aprobacià ³n de la peticià ³n suele tardar una media de cuatro meses. El ajuste de estatus, y con à ©l la tarjeta de residencia, se puede demorar entre seis meses y un aà ±o. Mientras se espera es posible solicitar un permiso de trabajo para el beneficiario y para su cà ³nyuge. Hay que destacar que las personas en situacià ³n de ilegalidad migratoria no pueden ajustar su estatus por esta causa. Solicitante fuera de Estados Unidos El proceso se inicia de igual manera: enviando al USCIS la forma I-140. Adems habr que enviar el formulario DS-230 para que una vez que se apruebe la solicitud los papeles (unos cuatro meses) estos se envà ­en a la oficina consular en el extranjero donde se tramitarn las green card para el solicitante y su familia. En casos de paà ­ses con un nà ºmero elevado de inmigrantes en Estados Unidos, como por ejemplo China o India Filipinas, o Mà ©xico, es posible que haya que esperar incluso aà ±os antes de poder completar todo el proceso. Ello se debe a que hay un là ­mite global anual de residencias que se pueden conceder por este motivo y un mximo de green cards de este tipo que se conceden por paà ­s. Para tener una estimacià ³n ms clara de cunto hay que esperar en el extranjero por la tarjeta de residencia una vez que se tiene la aprobacià ³n del USCIS lo mejor es consultar el Boletà ­n de Visas del Departamento de Estado.  (En ese enlace puedes ver hacia el final los tiempos de espera que aplican para este caso). Problemas, opciones y cosas que conviene saber Es posible que el USCIS no apruebe la solicitud de green card por cualquiera de estas causas que convierten a una persona en inadmisible en Estados Unidos. Las personas con habilidades excepcionales que no cumplen los requisitos para obtener una green card mediante patrocinio (EB-2) o sin patrocinio (EB-2 NIW) todavà ­a tienen opcià ³n para conseguir un visado. La visa O es la que aplica para estos casos. En el caso de emprendedores,  estas son 8 opciones de visa para crear una empresa en Estados Unidos. Adems, todas las personas que estn considerando la posibilidad de emigrar a los Estados Unidos pueden ahorrarse muchas sorpresas y problemas si se familiarizan e informan cuanto antes sobre aspectos migratorios y legales del paà ­s. Finalmente, se recomienda tomar este  trivial o test- para asegurar saber  cà ³mo conseguir la tarjeta de residencia  y cà ³mo conservarla. Este es un artà ­culo informativo. No es asesorà ­a legal.

Sexuality and violence Essay Example | Topics and Well Written Essays - 250 words

Sexuality and violence - Essay Example A perfect example took place in 1931 with the Scottsboro Boys case (Pratt, 2010): two police runaway women, Bates, a minor and Prince, an adult, claimed to have been raped by black Americans after a fight between two gangs; blacks and whites after they were discovered to be wearing men’s attire by officials. A crowd was waiting at the train terminus in Alabama to lynch the nine black men arrested of the rape act but the National Guard Forces prevented it. Nevertheless, they were tried by a white jury and found guilty labeling the crime as the most heinous against whites. A second example is the Central Park Jogger case where the victim, Trisha Meili was raped and beaten severely leaving her in a coma and without memory of what happened. Police assumed that the crime was committed by several Latinos and black Americans. Consequently, an arrest of five men followed and all were imprisoned. In 2003, Matias Reyes, one of the five convicts confessed to have committed the crime alone and despite a match in DNA evidence collected, the initial prosecutor verbally opposed cancelling of the initial convictions. Furthermore, a panel of police from New York City Police Department claimed that the initial number of suspects (five) was guilty. ii. The accused are assumed to be guilty (Davis, 1981). For instance, Prince claimed to have been raped by twelve black men and instead of police looking for the twelve men specifically, all black Americans on the train were taken captive. Similarly, Meili’s case saw Matias confess of being guilty yet the other four convicts were not voided and still assumed guilty. In both cases, the victims were imprisoned despite the court failing to find sufficient evidence. From the non-white point of view, the harsh decisions made against the four men in the Meili’s case led them to believe that any sexual activity against a white woman will be considered the most heinous of

Four Questions Assignment Example | Topics and Well Written Essays - 1500 words

Four Questions - Assignment Example In much of the considerations and analysis of the international system, experts would always make reference to World War I, World War II and the cold war. Occurrences that resulted in these three wars can be used to explain the basis of international world order and the establishment of the international system. O’rourke & Williamson, (2004) gives a broader look at the History of Diplomacy inn their work When did globalization begin? In submissions made in this piece, the authors assert that three great wars a reflection of how the international system considered a state-centric. The treaties signed and alliances formed during the three great wars were attempts by nations of the world in taking control of world affairs. In the history of diplomacy and international relations, states have remained to be a key force in determination of world politics. Just before the First World War, the concept of realism was borne, bringing to the fore an objective and critical analysis on the need for world order. In this respect, the international system was analyzed on the basis of both collective interests and the interests of certain states. Realists are of the opinion that state actors in the international world system can be identified on the basis of sovereignty, recognition of statehood, and the control of territory and population. From this perspective, countries cannot be ignored when defining the international system. From a realist perspective, the international system is a product of various historical occurrences, most on which took place in the twentieth century. The First World War was a major factor that brought out the need for a global or international-based system. As many countries in the European continue began fighting for colonies during the imperial era in Europe, conflic5ts between and amongst these countries emerged. Most of the countries started looking beyond national influence to influence within a wider geographical area. The consequence o f such rivalry was the development of the First World War. The development of two groups, the Central Powers and the Allies, during the war was pegged on superiority fight between nations that believed they could command or have great influence in world affairs. The end of the First World War was major milestone in the development of the international system as the allies went forth to instill heavy punishment to the Central Powers, led by Germany. The effects of the war were so serious that the League of Nations was formed so as to help avert such magnitude of conflict and war. The Second World War had also its share on development of the state centric International system. After the League of Nations failed, World War I was inevitable. The United States, Britain and France as the winners of World War II played a bigger role than other nations in the preparation of background for the formation of the modern day United Nations. By the United Nations and Russia awarding their selves with veto power in the world body, they had an edge over other countries. The state-centric nature of the world’s system would not be stopped here as even after the formation of the United Nations, the United States and the Soviet Union would still engage in supremacy tactics that is famously regarded as the cold war. Today, the United States remains to be the single most super power after the collapse of the USSR Richardson (2006) asserts that the United States

An operational amplifier

An operational amplifier Introduction: Anoperational amplifier, which is often called anop-amp, is aDC-coupledhigh-gainelectronic voltageamplifierwith a differential input and, usually, a single-ended output.An op-amp produces an output voltage that is typically millions of times larger than the voltagedifferencebetween its input terminals. Typically uses of the operational amplifier are to provide voltage amplitude changes (amplitude and polarity), oscillators, filter circuits, and many types of instrumentation circuits. An op-amp contains a number of differential amplifier stages to achieve a very high voltage gain. Typically the op-amps very large gain is controlled bynegative feedback, which largely determines the magnitude of its output voltage gain in amplifier applications, or thetransfer functionrequired. Without negative feedback, and possibly withpositive feedbackforregeneration, an op-amp essentially acts as acomparator. High inputimpedanceat the input terminals and low output impedance at the output terminals (ideally zero) are important typical characteristics. Op-amps are among the most widely used electronic devices today, being used in a vast array of consumer, industrial, and scientific devices. Many standard IC op-amps cost only a few cents in moderate production volume; however some integrated or hybrid operational amplifiers with special performance specifications may cost over $100 US in small quantities. Op-amps sometimes come in the form of macroscopic components, or asintegrated circuitcells; patterns that can be reprinted several times on one chip as part of a more complex device. The op-amp is one type ofdifferential amplifier. Other types of differential amplifier include thefully differential amplifier(similar to the op-amp, but with two outputs), theinstrumentation amplifier(usually built from three op-amps), theisolation amplifier(similar to the instrumentation amplifier, but with tolerance to common-mode voltages that would destroy an ordinary op-amp), andnegative feedback amplifier(usually built from one or more op-amps and a resistive feedback network). An Amplifier is made of: A Gain Block (ideally possessing infinite gain) Feedback A Network that sets the amount of feedback (e.g. resistors) The circuit symbol for an op-amp is shown to the right, where: The power supply pins (V_{text{S}!+}andV_{text{S}!-}) can be labelled in different ways). Despite different labelling, the function remains the same to provide additional power for amplification of signal. Often these pins are left out of the diagram for clarity, and the power configuration is described or assumed from the circuit. Op amps are versatile ICs that can perform a variety of mathematical functions. For this reason, they are the building blocks of many signal processing circuits. They have almost infinite gain, high input impedance, and low output impedance. Because of this, there is no current drawn at either input, and the voltage at both inputs must be equal (they are often drawn with a short connecting them) Op amps have two inputs, an inverting (-) and non inverting (+). A positive voltage source and negative voltage source or ground are connected directly to the op amp, although these are rarely shown on circuit diagrams. There is a single output, which is almost always connected to the inverting input with a feedback loop. Ideal Op Amps: There are three rules for analyzing op amp circuits. In addition to KVL and KCL, any op amp circuit should be solvable with these rules. Infinite input impedance. No current is drawn so: Infinite gain. This means that the input voltages must be equal. Zero output impedance. This means that output voltage does not depend on the output current. Real Op Amps: Ideal op amps are modelled with infinite gain and infinite impedance. While real op amps have high gain and low impedance, they are not infinite. This limiting factor can affect the performance of the circuit, so it should be considered. Another limitation of real op amps is voltage gain. Instead of being infinite, the maximum output voltage is about 1.4 V lower than the supply voltage (this is due to diode drops in the op amp). Ideal behaviour is not an accurate modelling technique when square waves are used. For this type of input, the voltage changes infinitely fast as it jumps from the high to the low parts of the wave. Op amps cant change instantaneously, there is a slight slope produced in the output. This can be measured by the slew rate (with is the change in voltage over the change in time). Rise time is another parameter used to calculate how quickly an op amp can adjust. The amount of time it takes the voltage to change from 10% to 90% of the desired value is the rise time. For application with square wave input, these two factors can affect the response of your circuit. Connecting an Op Amp: Op amps with Dual in Line Packages should be connected to a breadboard as shown here. The notch is at the top of the op-amp, with pins counted counter clockwise from the upper left corner. Operation: The amplifiers differential inputs consist of V_{!+}input and aV_{!-}input, and ideally the op-amp amplifies only the difference in voltage between the two, which is called thedifferential input voltage. The output voltage of the op-amp is given by the equation, WhereV_{!+}the voltage at the non-inverting terminal is,V_{!-}is the voltage at the inverting terminal andGopen-loopis theopen-loopgain of the amplifier. (The term open-loop refers to the absence of a feedback loop from the output to the input.) Op-amp with inverting input grounded through a resistor; input at the non-inverting input, and no feedback With no negative feedback, the op-amp acts as a switch. The inverting input is held at ground (0 V) by the resistor, so if the Vinapplied to the non-inverting input is positive, the output will be maximum positive, and if Vinis negative, the output will be maximum negative. Since there is no feedback from the output to either input, this is anopen loopcircuit. The circuits gain is just the Gopen-loopof the op-amp. Standard two-resistor non-inverting amplifier circuit The magnitude ofGopen-loopis typically very large-seldom less than a million-and therefore even a quite small difference betweenV_{!+}andV_{!-}(a few microvolts or less) will result in amplifier saturation, where the output voltage goes to either the extreme maximum or minimum end of its range, which is set approximately by the power supply voltages.Finleys lawstates that When the inverting and non-inverting inputs of an op-amp are not equal, its output is in saturation. Additionally, the precise magnitude ofGopen-loopis not well controlled by the manufacturing process, and so it is impractical to use an operational amplifier as a stand-alonedifferential amplifier. If linear operation is desired,negative feedbackmust be used, usually achieved by applying a portion of the output voltage to the inverting input. The feedback enables the output of the amplifier to keep the inputs at or near the same voltage so that saturation does not occur. Another benefit is that if much negative feedb ack is used, the circuits overall gain and other parameters become determined more by the feedback network than by the op-amp itself. If the feedback network is made of components with relatively constant, predictable, values such as resistors, capacitors and inductors, the unpredictability and inconstancy of the op-amps parameters (typical of semiconductor devices) do not seriously affect the circuits performance. If no negative feedback is used, the op-amp functions as a switch or comparator. Positive feedback may be used to introducehysteresisor oscillation. Returning to a consideration of linear (negative feedback) operation, the high open-loop gain and low input leakage current of the op-amp imply two golden rules that are highly useful in analysing linear op-amp circuits. Golden rules of op-amp negative feedback Ifthere is negative feedback andifthe output is not saturated, both inputs are at the same voltage; no current flows in or out of either input. These rules are true of the ideal op-amp and for practical purposes are true of real op-amps unless very high-speed or high-precision performance is being contemplated (in which case account must be taken of things such as input capacitance, input bias currents and voltages, finite speed, and otherop-amp imperfections, discussed in a later section.) As a consequence of the first rule, theinput impedanceof the two inputs will be nearly infinite. That is, even if the open-loop impedance between the two inputs is low, the closed-loop input impedance will be high because the inputs will be held at nearly the same voltage. This impedance is considered as infinite for an ideal opamp and is about onemegaohmin practice. Ideal and real op-amps: An equivalent circuit of an operational amplifier that models some resistive non-ideal parameters. An ideal op-amp is usually considered to have the following properties, and they are considered to hold for all input voltages: Infiniteopen-loop gain(when doing theoretical analysis, alimitmay be taken as open loop gainGgoes to infinity) Infinite voltage range available at the output (vout) (in practice the voltages available from the output are limited by the supply voltagesV_{text{S}!+}andV_{text{S}!-}) Infinitebandwidth(i.e., the frequency magnitude response is considered to be flat everywhere with zerophase shift). Infiniteinput impedance(so, in the diagram,R_{text{in}} = infty, and zero current flows fromv_{!+}tov_{!-}) Zero input current (i.e., there is assumed to be noleakageorbiascurrent into the device) Zeroinput offset voltage(i.e., when the input terminals are shorted so thatv_{!+}=v_{!-}, the output is avirtual groundor vout= 0). Infiniteslew rate(i.e., the rate of change of the output voltage is unbounded) and power bandwidth (full output voltage and current available at all frequencies). Zerooutput impedance(i.e.,Rout= 0, so that output voltage does not vary with output current) Zeronoise InfiniteCommon-mode rejection ratio(CMRR) InfinitePower supply rejection ratiofor both power supply rails. In practice, none of these ideals can be realized, and various shortcomings and compromises have to be accepted. Depending on the parameters of interest, a real op-amp may be modelled to take account of some of the non-infinite or non-zero parameters using equivalent resistors and capacitors in the op-amp model. The designer can then include the effects of these undesirable, but real, effects into the overall performance of the final circuit. Some parameters may turn out to havenegligibleeffect on the final design while others represent actual limitations of the final performance that must be evaluated. History: 1941: First (vacuum tube) op-amp An op-amp, defined as a general-purpose, DC-coupled, high gain, inverting feedbackamplifier, is first found in US Patent 2,401,779 Summing Amplifier filed by Karl D. Swartzel Jr. of Bell labs in 1941. This design used threevacuum tubesto achieve a gain of 90dB and operated on voltage rails of  ±350V. It had a single inverting input rather than differential inverting and non-inverting inputs, as are common in todays op-amps. ThroughoutWorld War II, Swartzels design proved its value by being liberally used in the M9artillery directordesigned at Bell Labs. This artillery director worked with the SCR584radarsystem to achieve extraordinary hit rates (near 90%) that would not have been possible otherwise. 1947: First op-amp with an explicit non-inverting input In 1947, the operational amplifier was first formally defined and named in a paper by Professor John R. Ragazzini of Columbia University. In this same paper a footnote mentioned an op-amp design by a student that would turn out to be quite significant. This op-amp, designed by Loebe Julie, was superior in a variety of ways. It had two major innovations. Its input stage used a long-tailedtriode pair with loads matched to reducedriftin the output and, far more importantly, it was the first op-amp design to have two inputs (one inverting, the other non-inverting). The differential input made a whole range of new functionality possible, but it would not be used for a long time due to the rise of the chopper-stabilized amplifier. 1949: First chopper-stabilized op-amp In 1949, Edwin A. Goldberg designed achopper-stabilized op-amp.This set-up uses a normal op-amp with an additionalACamplifier that goes alongside the op-amp. The chopper gets an AC signal fromDCby switching between the DC voltage and ground at a fast rate (60Hz or 400Hz). This signal is then amplified, rectified, filtered and fed into the op-amps non-inverting input. This vastly improved the gain of the op-amp while significantly reducing the output drift and DC offset. Unfortunately, any design that used a chopper couldnt use their non-inverting input for any other purpose. Nevertheless, the much improved characteristics of the chopper-stabilized op-amp made it the dominant way to use op-amps. Techniques that used the non-inverting input regularly would not be very popular until the 1960s when op-ampICsstarted to show up in the field. In 1953, vacuum tube op-amps became commercially available with the release of the model K2-W from George A. Philbrick Researches, Incorporated. The designation on the devices shown, GAP/R, is a contraction for the complete company name. Two nine-pin 12AX7 vacuum tubes were mounted in an octal package and had a model K2-P chopper add-on available that would effectively use up the non-inverting input. This op-amp was based on a descendant of Loebe Julies 1947 design and, along with its successors, would start the widespread use of op-amps in industry. 1961: First discrete IC op-amps With the birth of thetransistorin 1947, and the silicon transistor in 1954, the concept of ICs became a reality. The introduction of theplanar processin 1959 made transistors and ICs stable enough to be commercially useful. By 1961, solid-state, discrete op-amps were being produced. These op-amps were effectively small circuit boards with packages such as edge-connectors. They usually had hand-selected resistors in order to improve things such as voltage offset and drift. The P45 (1961) had a gain of 94dB and ran on  ±15V rails. It was intended to deal with signals in the range of  ±10V. 1962: First op-amps in potted modules By 1962, several companies were producing modular potted packages that could be plugged intoprinted circuit boards. These packages were crucially important as they made the operational amplifier into a singleblack boxwhich could be easily treated as a component in a larger circuit. 1963: First monolithic IC op-amp In 1963, the first monolithic IC op-amp, the  µA702 designed byBob Widlarat Fairchild Semiconductor, was released. MonolithicICsconsist of a single chip as opposed to a chip and discrete parts (a discrete IC) or multiple chips bonded and connected on a circuit board (a hybrid IC). Almost all modern op-amps are monolithic ICs; however, this first IC did not meet with much success. Issues such as an uneven supply voltage, low gain and a small dynamic range held off the dominance of monolithic op-amps until 1965 when the  µA709 was released. 1966: First varactor bridge op-amps Since the 741, there have been many different directions taken in op-amp design.Varactorbridge op-amps started to be produced in the late 1960s; they were designed to have extremely small input current and are still amongst the best op-amps available in terms of common-mode rejection with the ability to correctly deal with hundreds of volts at their inputs. 1968: Release of the  µA741 The popularity of monolithic op-amps was further improved upon the release of the LM101 in 1967, which solved a variety of issues, and the subsequent release of the  µA741 in 1968. The  µA741 was extremely similar to the LM101 except that Fairchilds facilities allowed them to include a 30pF compensation capacitor inside the chip instead of requiring external compensation. This simple difference has made the 741thecanonical op-amp and many modern amps base their pin out on the 741s.The  µA741 is still in production, and has become ubiquitous in electronics-many manufacturers produce a version of this classic chip, recognizable by part numbers containing741. 1970: First high-speed, low-input current FET design In the 1970s high speed, low-input current designs started to be made by usingFETs. These would be largely replaced by op-amps made withMOSFETsin the 1980s. During the 1970s single sided supply op-amps also became available. 1972: Single sided supply op-amps being produced A single sided supply op-amp is one where the input and output voltages can be as low as the negative power supply voltage instead of needing to be at least two volts above it. The result is that it can operate in many applications with the negative supply pin on the op-amp being connected to the signal ground, thus eliminating the need for a separate negative power supply. The LM324 (released in 1972) was one such op-amp that came in a quad package (four separate op-amps in one package) and became an industry standard. In addition to packaging multiple op-amps in a single package, the 1970s also saw the birth of op-amps in hybrid packages. These op-amps were generally improved versions of existing monolithic op-amps. As the properties of monolithic op-amps improved, the more complex hybrid ICs were quickly relegated to systems that are required to have extremely long service lives or other specialty systems. Recent trends Recently supply voltages in analog circuits have decreased (as they have in digital logic) and low-voltage op-amps have been introduced reflecting this. Supplies of  ±5V and increasingly 5V are common. To maximize the signal range modern op-amps commonly have rail-to-rail inputs (the input signals can range from the lowest supply voltage to the highest) and sometimes rail-to-rail outputs. A very typical commercial IC op amp circuit is the 741. This IC has been available for many years, and a number of variations have been developed to help minimize the errors inherent in its construction and operation. Nevertheless, the analysis we will perform here using the 741 will apply to any other IC op amp, if you take into account the actual parameters of the device you are actually using. Therefore, we will use the 741 as our example IC op amp. A differential amplifier connected as an op amp. To the right is a circuit using the 741 op amp IC, with the input and feedback resistors that are required for this circuit to operate properly in an analog computer. Note that there are actually two inputs to the amplifier, designated + and - in the figure. This is because the 741, like all IC op amps of this type, is in fact a differential amplifier. Thus, the output voltage is determined by thedifferencebetween the two input voltages. The +, or non-inverting input, is grounded through a resistor as shown. Thus, its input voltage is always zero. The -, or inverting input, is the one that is actively used. Thus, we establish that the inverting input, which is also the junction of the input and feedback resistors, must operate as a virtual ground in order to keep the output voltage within bounds. So far, so good, but what about the actual voltage gain? It cant possibly be infinite, and if it isnt infinite, there must be some non-zero input voltage to produce a non-zero output voltage. In fact, the typical open-loop voltage gain for the 741 is 200,000. This does not mean that every such device has a gain of 200,000, however. What is guaranteed is that the commercial version (the 741C) will have a minimum gain of 20,000. The military version is more stringently selected, and will have a minimum voltage gain of 50,000. For the 741C, then, with a maximum output voltage of  ±10 volts, the maximum input voltage required at the inverting input can never be more than  ±10/20,000 =  ±0.0005 volt, or 0.5 milli volts. Typical measurement accuracy uses three significant digits, so we would measure voltages from 0.00 volts to  ±10.00 volts. The maximum input voltage is more than an order of magnitude smaller than this, and hence is insignificant in a typical analog computer. But what about input bias current? Surely the IC requires at leastsomesmall amount of input current? Well, yes, it does. The 741C requires a typical input bias current of 80 nA (thats nano Amperes, where 1nA=10-9A). The maximum input bias current for the 741C is 500nA, or 0.5 µA. So how do we use this information to minimize the errors it could cause into insignificance? Well, lets consider the resistance that would be required for this current to cause a significant voltage drop. If we keep the voltage error small enough, we can ignore it as immeasurable. This means we must keep the values of Rinand Rfas small as possible, consistent with proper operation of the circuit. At the same time, we cannot make them too small, or the op amp itself will be overloaded. For proper operation, the total load resistance at the 741 output should not be smaller than 2000 ohms, or 2k. This amounts to a maximum output current of 5 mA at 10 volts output. This means that the output resistance of the op amp is not the desired zero ohms. However, as long as you dont draw too much current from the output, the use of heavy negative feedback has an added benefit: It makes the op amp behaveas ifit had zero output resistance. That is, any internal resistance will simply mean that the op amp must produce an internal voltage enough higher than the calculated value so that the final output voltage will be the calculated value. So what if we make our input and feedback resistors about 10k each? Then the current demand on the output is only 1 mA at 10 volts, leaving plenty of capacity for additional inputs. And the voltage caused by the input bias current wont exceed 10,000-0.5-10-6=0.005volt. This is half of the least significant digit of our measurement capability, which is not as good as we would like, but will do. Also, this is the absolute worst-case situation; most practical applications wont see an error this big. In addition, the input bias current applies equally to both inputs. This is the reason for the resistor connecting the + input to ground. If this resistor is close in value to the parallel combination of Rin and Rf, the same voltage error will be generated at the two inputs, and will therefore be cancelled out, or very nearly. Thus, we can relegate this problem to true insignificance by means of correct circuit design and careful choice of component values. The 741 does also have two error characteristics, calledinput offset voltageandinput offset current, which define the inherent errors which may exist between the two inputs to the IC. However, the 741 also has the means for balancing these variations out, so the actual errors are minimized or eliminated, thus once again removing them from significance. A problem with any op amp is a limited frequency response. The higher the gain of the complete circuit, the lower the working frequency response. This is one reason an overall gain of 20 is a practical limit. (Another reason is that the input and feedback resistors become too different from each other.) Also, the standard 741 has aslew rateof 0.5v/ µs. This means that the output voltage cannot change any faster than this. The newer generation of op amps, such as the 741S, have a slew rate more like 5v/ µs, and hence can operate over the entire audio range of frequencies without serious problems. Classification of Operational Amplifier: Op-amps may be classified by their construction: discrete (built from individualtransistorsortubes/valves) IC (fabricated in anIntegrated circuit) most common hybrid IC op-amps may be classified in many ways, including: Military, Industrial, or Commercial grade (for example: the LM301 is the commercial grade version of the LM101, the LM201 is the industrial version). This may defineoperating temperatureranges and other environmental or quality factors. Classification by package type may also affect environmental hardiness, as well as manufacturing options;DIP, and other through-hole packages are tending to be replaced bySurface-mount devices. Classification by internal compensation: op-amps may suffer from high frequencyinstabilityin somenegative feedbackcircuits unless a small compensation capacitor modifies the phase- and frequency- responses; op-amps with capacitor built in are termedcompensated, or perhaps compensated forclosed-loopgains down to (say) 5, others: uncompensated. Single, dual and quad versions of many commercial op-amp IC are available, meaning 1, 2 or 4 operational amplifiers are included in the same package. Rail-to-rail input (and/or output) op-amps can work with input (and/or output) signals very close to the power supply rails. CMOSop-amps (such as the CA3140E) provide extremely high input resistances, higher thanJFET-input op-amps, which are normally higher thanbipolar-input op-amps. Other varieties of op-amp include programmable op-amps (simply meaning the quiescent current, gain, and bandwidth and so on can be adjusted slightly by an external resistor). Manufacturers often tabulate their op-amps according to purpose, such as low-noise pre-amplifiers, wide bandwidth amplifiers, and so on. Single-Ended Inputs With single-ended inputs you connect one wire from each signal source to the data acquisition interface the Micro link. The measurement is the difference between the signal and the ground or earth at the Micro link. This method relies on the signal source being grounded (earthed), and the signal sources ground and the Micro links ground having the same value. Differences in Ground Levels We think of the ground as a constant 0V, but in reality the ground, or earth, is at a different level in different places. The closer together the places, the more likely the ground level will be the same. Make a connection between two grounds and the difference in levels can drive large currents, known as earth or ground loops. This can lead to errors when using single-ended inputs. Noise Errors Single-ended inputs are sensitive to noise errors. Noise (unwanted signal contamination) is added because signal wires act as aerials, picking up environmental electrical activity. With single-ended inputs you have no way of distinguishing between the signal and the noise. The ground and noise problems can be solved by differential inputs. Differential Inputs With differential inputs, two signal wires run from each signal source to the Microlink. One goes to a + input and one to a input. Two high-impedance amplifiers monitor the voltage between the input and the interface ground. The outputs of the two amplifiers are then subtracted by a third amplifier to give the difference between the + and inputs, meaning that any voltage common to both wires is removed. This can solve both of the problems caused by single-ended connections. It means that differences in grounds are irrelevant (as long as they arent too large for the amplifier to handle). It also reduces noise twisting wires together will ensure that any noise picked up will be the same for each wire. Floating Signals A common problem when using differential inputs is neglecting any connection to ground. For example, battery-powered instruments and thermocouples have no connection to a buildings ground. You could connect a battery, for instance, between the Micro links + and inputs. The 2 input amplifiers will try to monitor the voltages + to earth and to ground. However, as there is no connection between the battery and ground, these voltages to ground could be any value and may be too large for the amplifier to handle. For these floating signal sources you should provide a reference. The Micro link has a socket labelled 0V. Run a wire from, say, the wire to this OV socket, either directly or via a resistor. (If your signal source is itself grounded dont make a connection to the Micro links 0V socket.) Amplifier Ability and Operating Range The three amplifiers used for differential inputs are collectively known as an instrumentation amplifier. Ideally, as previously described, any voltage common to both wires (common mode voltage) is cancelled. In practice the two input amplifiers are not perfectly matched so a fraction of the common mode voltage may appear. How closely the instrumentation amplifier approaches the ideal is expressed as the common mode rejection ratio (CMRR). This is the reciprocal of the fraction let through and is usually given in decibels. The higher the rejection ratio the better. Another specification to look for is the common mode range. This is the maximum contamination voltage with which the amplifier can cope. If the difference in ground levels between your interface and signal source exceeds this value, your measurement will be inaccurate. Less Signals with Differential Inputs? An obvious disadvantage of differential inputs is that you need twice as many wires, so you can connect only half the number of signals, compared to single-ended inputs. Should you decide that single-ended inputs are OK for you if you have short signal wires, close together signal sources, and signals larger than around 100 mV for e.g. you can use differential inputs in single-ended mode. To do this short one of the signal wires (usually the input) to the Micro link V input. Differential inputs, therefore, give you the option of either mode. Op-Amp Characteristics: A very typical commercial IC op amp circuit is the 741. This IC has been available for many years, and a number of variations have been developed to help minimize the errors inherent in its construction and operation. Nevertheless, the analysis we will perform here using the 741 will apply to any other IC op amp, if you take into account the actual parameters of the device you are actually using. Therefore, we will use the 741 as our example IC op amp. A differential amplifier connected as an op amp. To the right is a circuit using the 741 op amp IC, with the input and feedback resistors that are required for this circuit to operate properly in an analog computer. Note that there are actually two inputs to the amplifier, designated + and - in the figure. This is because the 741, like all IC op amps of this type, is in fact a differential amplifier. Thus, the output voltage is determined by thedifferencebetween the two input voltages. The +, or non-inverting input, is grounded through a resistor as shown. Thus, its input voltage is always zero. The -, or inverting input, is the one that is actively used. Thus, we establish that the inverting input, which is also the junction of the input and feedback resistors, must operate as a virtual ground in order t