A power amplifier

A power amplifier Introduction: A power amplifier is an electronic device that changes the magnitude of a signal. It is usually used to transfer high power to a low output load such as speakers where there load is about 8 ohms [1]. The relationship between the output and input is called the transfer function. An important aspect of the amplifier is the gain. The gain is the ratio between input and output whether this input is current, voltage or power. Therefore, the gain does not have a unit. The quality of the amplifier is determined by many aspects, which are gain, bandwidth, efficiency, linearity, noise and others. As one of these characteristics increase the others may decrease. Therefore, the amplifier will be designed to meet the required specifications determined by the application for which it will be used for. The various designs of the amplifiers are classified into many types which include A,B,C,D and some other types derived by combining the basic ones such as class AB which is obtained from class A and class B pertaining to their efficiency and linearity [1]. Ideally, power amplifiers are supposed to deliver 100% of the power to the load. However, as some of the power dissipates in the components of the amplifier, hence we do not have ideal power amplifiers. It is found that the linearity has an inverse relationship to the efficiency of the amplifier. The classes A, B and C power amplifiers are considered inefficient but linear whereas the other types are considered efficient but more complex than the basic types. Class A power amplifiers are least efficient than the others. The efficiency of class B is much higher than class A, however, class C has the highest efficiency level compared to class A and B [2]. The scope of this paper is to discuss class B power amplifier in details. Class B power amplifier: This class of amplifier was developed in order to improve class A power amplifiers, which have low efficiency rating. [1-3] shows and explains the internal desig n, the efficiency, the advantages and disadvantages, and the applications of class B power amplifiers. Internal circuit and operation: To get a sufficiently good amplification of the input waveform in the output, a push-pull class B power amplifier configuration must be used. This configuration is based on two transistors. The term push-pull comes from the fact that two transistors in a class B amplifier conduct in alternating half-cycles of the input [1]. Moreover, there are two types of push-pull configurations, one with transformers and one without transformers [2]. A balanced centre tapped input transformer is used to split the incoming waveform signal into two equal cycles that are 180 degrees out of phase with each other. Another center-tapped output transformer is used to recombine the signals. If the transformer is ideal we can get two collector currents that flow in opposite directions, hence no magnetization of the transformer core takes place which in turn minimizes the d istortion in between the two signals. Both transistors used are of NPN transistor type where their emitter terminals are connected together [2].

Reality TV Influence on the Audience Essay Example | Topics and Well Written Essays - 1250 words

Reality TV Influence on the Audience - Essay Example As the discussion stresses  during the initial years of the twenty first century, viewers watched reality TV to observe people’s lives, watch them argue, fight, eat bizarre things and reveal personal details of their lives. These reality shows were humored and harmless. But with time, the essence of reality TV has changed. People now participate in reality shows to contest against each other in order to win some prize or gain popularity. This reflects increased competitiveness and materialism prevailing in the society.  This research declares that  as television drama became more violent and sexually explicit, reality TV evolved as a more meaningful genre of TV shows that present viewers with more competitive and bitter versions closer to reality. Psychologists present interesting explanation as to why reality shows are very popular. One of the primary reasons is that viewers can identify themselves with the participants who are initially ordinary people and then become famous. Secondly, they enjoy the competitive nature of such shows since there are always winners and losers.  Reality TV is taking over regular TV and is polluting people’s mind. Violence, distorted pictures of reality, language and stunts are marking a lot of reality TV. These shows are very entertaining but many professionals are expressing concerns over the harmful implications. They point out that negative impacts of reality TV are higher for children and teenagers than adults.

The Snows of Kilimanjaro by Ernest Hemingway Research Paper

The Snows of Kilimanjaro by Ernest Hemingway - Research Paper Example 191). In other words, Hemmingway’s The Snows of Kilimanjaro tells a story about writing and somehow links this story to human themes. To demonstrate the point, Becnel and Bloom (2009) draw attention to the following passage narrated by Harry and taken from The Snows of Kilimanjaro: We must all be cut out for what we do, he thought. However, you make your living is where your talent lies. He had sold vitality, in one form or another, all his life and when you affections are not too involved you give much better value for the money. He had found that out but he would never write that, now, either. No, he would not write that, although it was well worth writing (Hemmingway 2003, p. 12). Becnel and Bloom (2009) noted that from Harry’s perspective, he acknowledges that during his life as a soldier, writer and husband married into wealth he has been â€Å"selling vitality† his entire life (p. 191). Therefore Harry is able to connect the demands and passions in life via three seemingly unrelated factors: marriage, the military and writing. The connection begs inquiry in to how each of these factors relate to selling vitality. It is therefore first necessary to understand what Harry means by selling his vitality. Looking further into The Snows of Kilimanjaro some guidance can be found in the following excerpt: He had destroyed his talent himself – by not using it, by betrayals of himself and what he believed in, by drinking so much that he blunted the edge of his perceptions, by laziness, by sloth, by snobbery, by hook and by crook; selling vitality, trading it for security, for comfort (Hemmingway 2003, p. 11). This excerpt informs that selling vitality means sacrificing one’s own talents and ambitions in favour of security and at times in favour of other human frailties: laziness, greed and other exigencies of human weaknesses. In many ways these human exigencies are seductions and inevitably forced Harry to trade the vital elements of his life for greater comforts (Bush 1995, p. 26). Arguably, Harry was unable to succeed at or find complete satisfaction via marriage, soldiering and writing because he had sought comfort and security rather than the art of mastering each of these factors. The selling of vitality from Harry’s perspective thus informs that Harry sold or surrendered something of significance in his marriage, soldiering and writing. He therefore loses something of importance in each of these life roles. That something must be passion as, he suggests that a man must make his living where his talent lies and for Harry, his talent lies in trading vitality or sacrificing his real ambitions in favor of shortcuts to comfort and security. The suggestion is therefore that Harry’s life is disingenuous or at the very least the reader can form the opinion that Harry is only superficially happy as he has sacrificed what he really wants out of life for comfort and security. He has also allowed his pursuits to be compromised by the seductions that lead to or command shortcuts. His marriage into wealth may perhaps demonstrate the point best as he has obviously succumbed to a shortcut to material possessions or the seductions inherent in sloth. Soldiering would obviously provide Harry with material for his