电子信息类专业英语(西电第二版)Unit-4-Microelectronics课件.ppt

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1、Unit 4 MicroelectronicsUnit 4 MicroelectronicsPassage A Introduction to Microelectronics Passage B The Simple Atom,Conductors,Insulators and Semiconductors Passage C Diode and Transistor Unit 4 MicroelectronicsPassage A Introduction to MicroelectronicsThe exploring of space and the development of ea

2、rth satellites has increased the importance of reducing the size and weight of electronic circuits.Also,even though electricity flows quite rapidly in computers the time delay of the signal in the interconnections between electronic components is an important consideration.If the interconnections ar

3、e reduced in size,a computer can perform operations at a faster speed.Microelectronics involves the miniaturization of regular electronic circuits.A complete electronic circuit,an operational amplifier for example,which contains large numbers of individual interconnected components,such as diodes re

4、sistors,transistors,etc.may be formed on a very small single substrate.The complete miniaturized circuit is then called an integrated circuit.Unit 4 MicroelectronicsIntegrated circuits are small,light,rugged,and reliable.They require less power and lower voltages than equivalent macroscopic circuits

5、;consequently they operate at lower temperatures,and individual components may be close together without exceeding the operating temperature limit.Relatively little stray capacitance and short time delays are produced because of the short interconnections between the individual components in IC.Main

6、tenance is simplified because if a component of the IC fails the complete IC is usually replaced.Mass production techniques of plane technology have reduced the cost of many IC so that they are almost as inexpensive as a single transistor.Eventually most conventional circuits will be replaced by IC.

7、Unit 4 MicroelectronicsThere are two types of basic integrated circuit:monolithic integrated circuit and the thin or thick film.Monolithic IC are constructed in a single substrate of single crystal semiconductor,usually silicon.Thin or thick films IC are formed on the surface of an insulating materi

8、al such as glass or a ceramic.Hybrid IC contains more than a single substrate,the term hybrid is also applied to combinations of monolithic and thin or thick film IC.Unit 4 MicroelectronicsUnit 4 MicroelectronicsMost electronic circuits are composed of active devices,e.g.transistors and diodes,toget

9、her with resistors(for bias,collector load,impedance transformation,etc.)and capacitors(e.g.for coupling ac signals while blocking dc supplies).Each of these elements can be produced in a form suitable for integrated circuit inclusion within limitations,e.g.capacitance values must not be too large.S

10、ome elements are difficult to produce in a suitable form,e.g.inductive elements,or large capacitors.Usually some alternative circuit form can be devised that dispenses with the requirement.Otherwise they must be included as an external lumped element.Unit 4 MicroelectronicsNotes1 Intergraded circuit

11、s are also classified according to their functions.Digital or logical IC are used as switches,they are either on or off.In computers the on and off states correspond to 0 or 1.Other IC is called linear or analog IC.也可根据其功能不同对集成电路进行分类。数字IC(也称为逻辑IC)通常用作开关,表示接通或关断。在计算机中,接通和关断状态分别对应“0”或“1”。另一种IC被称为线性或模拟

12、IC。either.or.表示两者择一,在文中译为“要么要么”。Unit 4 Microelectronics2 The reduction in power dissipation is particularly important where a complex circuit is to be concentrated into a small space.The problem of extracting the heat generated in the circuit may then be a difficult one.减小功率损耗是非常重要的,其方法是将一个复杂的电子线路集成

13、为一小块。这使得释放电路工作时产生的热量变成一个难题。The problem of.may then be a difficult one.文中的one表示强调这个问题,这种句式在科技英语中常被使用。extracting the heat 为释放热量的意思,extract的本意为“抽出,剥离”。在电子线路中,器件工作均会产生热量,如果不能及时散热,器件就不能稳定工作。Unit 4 MicroelectronicsUnit 4 Microelectronics2.Please translate the following sentences into Chinese.(1)It is assu

14、med that the reader has a general knowledge of circuit theory.(2)Which of these methods is determine Req depends upon which is the easiest in any given situation.(3)It is an experimental fact that an electric field is established in a conducting rod when there is a temperature difference between its

15、 ends.(4)That this condition is sufficient is obvious.Unit 4 Microelectronics(5)It can be shown that any rational function of sin x and cos x can be integrated.(6)A major advantage of this device is that it operates continuously.(7)In this chapter we shall determine which load receives the maximum p

16、ower for a given practical voltage source.Unit 4 MicroelectronicsUnit 4 MicroelectronicsElements contain smaller particles called atoms.In any one element the atoms are identical in structure.The difference between any two elements such as gold and mercury is in their atomic structures.They have in

17、common,however,a relatively heavy inner core called a nucleus surrounded by one or more extremely light particles of matter called electrons.The simplest nucleus is a mass of matter about 2,000 times the weight of an electron,and is called a proton.More complex nuclei contain various combinations of

18、 protons and neutrons.A neutron is a proton combined with an electron and is electronically neutral.Unit 4 MicroelectronicsUnit 4 MicroelectronicsAn atom,which has all of its orbital(rotating)electrons has as many positive charges and therefore the net charge is zero.When an atom loses an electron t

19、he balance of charge is disturbed and the atom becomes positively charged.In this condition,the atom is called a positive ion.In comparison,when an atom acquires an electron,the balance of charges is again disturbed and the atom becomes negatively charged,such an atom is referred to as a negative io

20、n.Unit 4 MicroelectronicsConductors,Insulators and SemiconductorsAny substance,which allows electrons to flow freely through its structure is called a conductor.In general,metals are good conductors.A definite relationship exists between good conductors and their atomic structures.In good conductors

21、,the outer-ring electrons,which are also called valence electrons,may be released from their orbits with relative ease.Atom with 1,2 and 3 outer ring electrons,and therefore most metals are good conductors.Unit 4 MicroelectronicsUnit 4 MicroelectronicsSemiconductors are a group of materials,which co

22、nduct electrons poorly and therefore cannot properly be classified either as conductors or insulators.Generally,semiconductors differ from insulators in that their outer-ring electrons can detach themselves from their orbits more easily than in insulators.Typical semiconductors materials are germani

23、um and silicon.Impurities may be added to pure semiconductors.This results in semiconductor materials,which may either have an excess of free electrons or a deficiency of orbital electrons.When an excess of electrons is present we call the material N-type;when lack of orbital electrons occurs,we cal

24、l the material P-type.Both N-type and P-type semiconductors are made by treated materials.such as germanium and silicon with impurities such as arsenic and indium.The addition of impurities to semiconductors is called doping.Unit 4 Microelectronics Notes1 Each element has a separate identity of its

25、own,that is,no two elements have the same physical and chemical properties,nor can an element be subdivided by ordinary physical and chemical means into simple elements.每一种元素均有它自己的标识,也就是说,没有两个元素具有相同的物理和化学特性,一种元素也不能以普通的物理或化学方法被分为两种简单的元素。that is是插入语。nor 也不,提到句首使用时,句子要倒装,表示强调。Unit 4 Microelectronics2 E

26、letrons whirl around nuclei in much the same manner that the planets of our solar system travel around the sun.The difference between an atom of one element and that of another is in the number of protons and neutrons contained in the nucleus.电子围绕原子核旋转,其方式类似于太阳系中行星围绕太阳旋转。一种元素的原子和另一种元素的原子的差别在于其原子核中的质

27、子数和中子数。in much the same manner that 中,in.manner意为“以的方式”,that是manner的定语从句。Unit 4 Microelectronics3 Both N-type and P-type semiconductors are made by treated materials,such as germanium and silicon with impurities such as arsenic and indium.N型半导体和P型半导体是利用杂质掺入纯净半导体而形成的,如将杂质砷和铟掺入锗和硅中。are made by treated

28、 material,treat原意为对峙,treated materials指前文将杂质掺入纯净半导体的过程。Unit 4 MicroelectronicsExercises1.True/False.(1)The materials that make up our universe are atoms.()(2)Generally we distinguish the elements by their atomic structures.Each atom has a unique identify.()(3)The atom is always composed of proton,ne

29、utrons and electrons.()(4)When the temperature is high,an electron can attract amount heat and then fly off into space.()(5)The semiconductor can permit the current through their body if some condition is supplied.()Unit 4 MicroelectronicsUnit 4 Microelectronics2.Translate the following sentences in

30、to English.(1)工科学生应该知道如何使用计算机。(2)物体做功的能力被称为能量。(3)重要的是我们要把理论应用于实践。(4)计算在这个电路中流动的电流密度是可能的。(5)这些是常用的设备。(6)电压等取决于电路中的电阻以及所加的电压。Unit 4 Microelectronics3.Translate the following sentences into Chinese.(1)These capacitors are commonly used where change in capacitance is necessary.(2)The advent of electroni

31、cs is reckoned from the discovery that the current in a vacuum diode can be controlled by introducing a third electrode.(3)The concept of work is so important that it will bear further discussion.(4)Just as good electrical conductors are also good conductors of heat,poor electrical conductors are al

32、so poor thermal conductors.Unit 4 Microelectronics(5)By the use of electrical insulators,electrical currents can be confined to well-designed paths in good electrical conductors,while it is impossible to confine heat currents to a comparable extent.(6)The statement that a man weighs 160 pounds is eq

33、uivalent to a statement that he is attracted by the earth with a force of 160 pounds.Unit 4 MicroelectronicsUnit 4 MicroelectronicsFigure4.1 The basic crystal junctionUnit 4 MicroelectronicsFigure4.2 Forward biased connection inUnit 4 MicroelectronicsUnit 4 MicroelectronicsWhen the polarity of the p

34、ower source is reversed,the semiconductor is said to be reverse biased.The holes are moved away from the junction by the negative voltage,whereas the electrons are draw from the junction by the positive voltage.Thus there is little or no combining of electrons and holes at the junction,and no curren

35、t will flow.In practical terms,there will always be a few electrons and holes near the junction,allowing a very small current to pass.This small current is known as leakage current and is usually in the order of a few microamperes(or possibly pico amperes).Unit 4 MicroelectronicsWhen P-type and N-ty

36、pe regions are formed in same crystal,the semiconductor is known as a diode or rectifier.The boundary between the two regions is termed a junction.The P-region terminal is called the anode,whereas the N-region terminal is called the cathode.Usually,when such semiconductors are used with signals,the

37、semiconductors are called diodes or signal diodes.When the device is used for conversion of alternating current(ac)to direct current(dc),the semiconductor is called a rectifier.Unit 4 MicroelectronicsBasic Two-junction or Bipolar TransistorLike a diode,a transistor can be used to prevent(or limit)th

38、e flow of current in one direction,The prime use for a transistor,however,is to control the amount of current in a circuit.This is done by adding a second junction to the basic diode junction,discussed in the above section.For this reason,such transistors are called two-junction transistors or,possi

39、bly,bipolar transistors.The author prefers the former term but recognizes that the latter term is also in common use.Unit 4 MicroelectronicsThere are two possible arrangements for the two-junction in transistors:NPN,where a positive semiconductor material(holes)is placed between two negative semicon

40、ductor materials(electrons),and PNP,where the negative material(electrons)is placed between two positive materials(holes).With either junction arrangement,the basic two-junction transistor will have three elements.These elements,show in Figure9.3 as an NPN arrangement,are the emitter,which emits ele

41、ctrons;the collector,which collects electrons;and a base,which controls the flow of electrons by controlling the charge concentration at the two-junctions on either side of the base.Unit 4 MicroelectronicsFigure4.3 NPN and PNP two-junction transistor arrangementsUnit 4 MicroelectronicsFigure9.4 show

42、s how two junction transistor operates in its basic circuit.As shown,the emitter-base junction will pass current easily because the junction is forward biased.The collector-base junction will not pass current(except for a small leakage current)since the junction is reverse biased.(The term back is o

43、ften used in place of reverse bias.)Unit 4 MicroelectronicsFigure4.4 Basic two-junction transistor bias circuitUnit 4 MicroelectronicsIt should be noted that the polarities of bias voltage for an NPN transistor differ from those of a PNP transistor;however,the net results are the same.For example,as

44、 shown in Figure9.4,the emitter is negative with respect to the base(NPN)to produce a forward bias.In Figure9.4,the emitter is positive with respect to base(PNP)to produce the same forward bias.Similarly,the collector has a reverse bias for both NPN and PNP,even though the polarities are revered.Als

45、o,it should be noted that for normal operation an NPN has its base biased positively with respect to its emitter.Conversely,a PNP base is negative with respect to its emitter.Unit 4 Microelectronics(a)Basic two-junction transistor operation.During normal operation of a two-junction transistor,curren

46、t will flow between emitter and base and between emitter and collector but not between collector and base.Most of the current flows between emitter and collector,because of the large voltage difference existing between these elements(the sum of the emitter-base voltage and the collector-base voltage

47、).This produces a large number of charge carriers(positive holes in a PNP or negative electrons in an NPN)that diffuse through this base region when passing from emitter to collector(or vice versa).Few of these charge carriers combine with the charge(positive in NPN,negative PNP)in the base.Unit 4 M

48、icroelectronicsMore charge carriers will be pulled out of the emitter and made available for the collector if the base-emitter current is increased.This can be accomplished by masking the base more negative in a PNP transistor or by making the base more positive in an NPN transistor.If the base-emit

49、ter voltage is decreased,less charge carriers will be pulled form the emitter and less emitter-collector current will flow.Unit 4 MicroelectronicsSince very little voltage(approximately 0.2V for germanium and 0.5V for silicon)is required to produce a large current flow in the emitter,input power to

50、a transistor is low.Most of the emitter current flows in the collector circuit,where the voltage is made much larger.As a result,a relatively large amount of power can be controlled in an external load(connected in series with the collector circuit)by a small amount of power in the emitter circuit.T