电气自动化专业英语3.ppt

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1、Chapter 1 Electric and Electronic Technology Fundamentals,Unit 3 Transistor,Text,New Words and Expressions,Exercises,End,Process of Translation,Unit3 Transistor,A transistor is a semiconductor device used to amplify and switch electronic signals.It is made of a solid piece of semiconductor material,

2、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 more than the controlling(input)power,the transistor

3、 provides amplification of a signal.Today,some transistors are packaged individually,but many more are found embedded in integrated circuits.,The transistor is the fundamental building block of modern electronic devices,and is ubiquitous in modern electronic systems.Following its release in the earl

4、y 1950s the transistor revolutionised the field of electronics,and paved the way for smaller and cheaper radios,calculators,and computers,amongst other things.,Unit3 Transistor,Importance The transistor is the key active component in practically all modern electronics,and is considered by many to be

5、 one of the greatest inventions of the twentieth century.Its importance in todays society rests on its ability to be mass produced using a highly automated process(semiconductor device fabrication)that achieves astonishingly low per-transistor costs.,Unit3 Transistor,Unit3 Transistor,Although severa

6、l companies each produce over a billion individually packaged(known as discrete)transistors every year,the vast majority of transistors now produced are in integrated circuits(often shortened to IC,microchips or simply chips),along with diodes,resistors,capacitors and other electronic components,to

7、produce complete electronic circuits.A logic gate consists of up to about twenty transistors whereas an advanced microprocessor,as of 2009,can use as many as 2.3 billion transistors(MOSFETs).About 60 million transistors were built this year 2002.for each man,woman,and child on Earth.,The transistors

8、 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 cont

9、rol function than to design an equivalent mechanical control function.,Unit3 Transistor,Transistor as a switch 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.In a grounded-emi

10、tter transistor circuit,such as the light-switch circuit shown,as the base voltage rises the base and collector current rise exponentially,and the collector voltage drops because of the collector load resistor.The relevantequations:,Unit3 Transistor,URC=ICERC,the voltage across the load(the lamp wit

11、hresistance Rc)URC+UCE=UCC,the supply voltage shown as 6V If UCE could fall to 0(perfect closed switch)then IC could go no higher than UCC/Rc,even with higher base voltage and current.The transistor is then said to be saturated.Hence,values of input voltage can be chosen such that the output is eith

12、er 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 valuesare relevant.,Unit3 Transistor,Unit3 Transistor,Transistor as an amplifier The common-emitter amplifier is designed so that a small change in v

13、oltage in(Vin)changes the small current through the base of the transistor and the transistors current amplification combined with the properties of the circuitmean that small swings in Uin produce large changes in Uout.Various configurations of single transistor amplifier are possible,with some pro

14、viding current gain,some voltagegain,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

15、 fidelity gradually increased as better transistors became available and amplifierarchitecture evolved.Modern transistor audio amplifiers of up to a few hundredwatts are common and relatively inexpensive.,Return,Unit3 Transistor,Unit3 Transistor,TypesTransistors are categorized bySemiconductor mater

16、ial:germanium,silicon,galliumarsenide,silicon carbide,etc.Structure:BJT,JFET,IGFET(MOSFET),IGBT,othertypes Polarity:NPN,PNP(BJTs);N-channel,P-channel(FETs)Maximum power rating:low,medium,high;Maximum operating frequency:low,medium,high,radio frequency(RF),microwave(The maximum effectivefrequency of

17、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 yieldsunity gain).,Unit3 Transistor,Application:switch,general purpose,audio,high voltage,super-beta,matched pair Physical packaging:through hole me

18、tal,through hole plastic,surface mount,ball grid array,power modules Amplification factor hfe(transistor beta)Thus,a particular transistor may be described as silicon,surface mount,BJT,NPN,low power,high frequency switch.,Unit3 Transistor,Packaging Through-hole transistors(tape measure marked in cen

19、timetres)Transistors come in many different packages(semiconductor packages)(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 array

20、s).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.,Unit3 Transistor,Transistor packages are made of glass,metal,ceramic,or plastic.The package often dictates the

21、power rating and frequency characteristics.Power transistors have larger 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

22、 transistors are as small as grains of sand.Often a given transistor type is available in sundry packages.Transistor packages are mainly standardized,but the assignment of a transistors functions to the terminals is not:other transistor types can assign other functions to the packages terminals.Even

23、 for the same transistor type the terminal assignment can vary(normally indicated by a suffix letter to the part number,q.e.BC212L and BC212K).,New Words and Expressions,transistor n.晶体管 amplify vt.放大,增强ubiquitous adj.普遍存在的 calculator n.计算器astonishingly adv.令人吃惊地 discrete adj.不连续的,离散的MOSFET 金属氧化物半导体

24、场效应晶体管 flexibility n.弹性,适应性mechatronic n.机电一体化 electromechanical adj.机电的saturate v.使饱和,浸透,使充满 milliwatt n.毫瓦gallium arsenide 砷化镓 silicon carbide 碳化硅BJT 双极结型晶体管(Bipolar Junction Transistor)JFET 结晶型场效应晶体管(junction field effect transistor)IGFET 绝缘栅场效应晶体管(isolated-gate field effect transistor)IGBT,绝缘栅双极

25、型晶体管(Insulated Gate Bipolar Transistor)N-channel n沟道 abbreviation n.缩写,缩写词denote vt.指示,表示 yield v.出产,生产super-beta 高倍放大 matched pair 推挽式放大through hole 透眼,透孔 surface mount 面封装式ball grid array 球栅阵列(封装)power module 功率模块(封装)amplification factor 放大倍数 centimeter n.厘米,公分package n.包装，封装 ceramic n.陶瓷collector

26、 n.集电极 drain n.漏极grain n.谷粒,细粒 sundry adj.各式各样的assignment n.分配,安排 suffix n.后缀,下标,Return,Process of Translation,理解阶段 主要是通过辨明词义，弄清各种语法成分及其相互关系，并把前后句子贯串起来理解，形成对原文的完整印象，真正掌握原文的内容和实质。,表达阶段 是在理解的基础上，以忠实于原意为前提，灵活地运用各种翻译方法和技巧，写出符合汉语规范、表达习惯以及翻译标准的译文。,校核阶段 是理解与表达的进一步深化，是对原文内容进一步核实，对译文语言进一步推敲，进行必要的润色和修改，使译文符合标

27、准规范。,Exercises,I.Comprehension,1.Transistors are commonly used as electronic _,for both high power applications including swiched-mode power supplies and low powerapplications such as logic gates.A.heaters B.transformers C.amplifiers D.switches 2.This arrangement where the emitter(E)is in the contro

28、lling circuit(base current)and in the controlled circuit(collector current)is called _.A.common collector mode B.common base modeC.common emitter mode D.all,Exercises,3.Which of the following statements is not true about functional model of transistor?_A.The base-emitter junction behaves like a diod

29、e.B.The small base current IB controls the large collector IC.C.The collector current IC is controlled by the base current IB.D.A base current IB flows only when the voltage UBE across the base-emitter junction is less than 0.7 V.4.When a transistor works as an amplifier,its large collector current

30、IC is _ the base current IB.A.more than B.less than C.proportional to D.equal to,I.Comprehension,Exercises,5.The transistor should operate within a _ portion of the graph,otherwise the output signal will suffer distortion.A.nonlinear B.linear C.cut-off D.saturation,I.Comprehension,Return,Unit 3 End,