1、Unit Nine Microelectronics,Passage A Introduction to Microelectronics Passage B The Simple Atom, Conductors, Insulators and Semiconductors Passage C Diode and Transistor,Passage A Introduction to MicroelectronicsThe exploring of space and the development of earth satellites has increased the importa
2、nce 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 are reduced in size, a computer can per
3、form 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 resistors, transistors, etc. may b
4、e formed on a very small single substrate. The complete miniaturized circuit is then called an integrated circuit.,Integrated circuits are small, light, rugged, and reliable. They require less power and lower voltages than equivalent macroscopic circuits; consequently they operate at lower temperatu
5、res, 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. Maintenance is simplified because if a compone
6、nt 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.,There are two types of basic integrated
7、 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 material such as glass or a ceramic. Hybrid IC contains more tha
8、n a single substrate, the term hybrid is also applied to combinations of monolithic and thin or thick film IC.,Integrated circuits 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
9、 0 or 1. Other IC is called linear or analog IC.1 Integrated circuits can be produced using either bipolar or unique polar transistors. Field effect transistors (FET) have a advantages over bipolar transistors in many cases however. They are relatively high-impedance devices, with a corresponding re
10、duction in current and power dissipation, and yet have high power gain. 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.2 The form of
11、 construction of the FET, and particularly the MOSFET, also lends itself well to integrated circuit fabrication, and enables resistors and capacitors to be included readily in the integrated circuit.,Most electronic circuits are composed of active devices, e.g. transistors and diodes, together with
12、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.
13、 Some 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.,KEY WORDS microelectronic 微电子 amplifier 放
14、大器 considerable 相当的; 重要的 substrate 基质; 底质 integrate 综合; 使完全 rug 地毯; 毯子 reliable 可靠 maintenance 维护; 保持; 维修 film 胶片; 薄膜 monolithic 独立的; 完全统一的 silicon 硅 hybrid 混合物 bipolar (电子)双极的,FET (Field effect transistors)场效应管 impedance 阻抗 dissipation 损耗 extractive 抽出; 释放出 fabrication 制造, 装配; 捏造事实 bias 偏差; 偏置 capa
15、citor 电容 inductive 电感 dispense 分配 lumped element 集总元件 transistor 晶体管,NOTES1 Integrated circuits 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
16、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IC。 eitheror表示两者择一，在文中译为“要么要么”。,2 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 genera
17、ted 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 ofmay 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。,Passage B The Simple Atom, Conduc
18、tors, Insulators and Semiconductors The Simple AtomThe materials that make up our universe are composed of over one hundred basic and individual types of matter called elements. Ninety-two of these elements occur naturally and the remainders are man-made. Each element has a separate identify of its
19、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.1 Examples of elements are gold, mercury and oxygen.,Elements contain smaller particles called atoms. In any one element the ato
20、ms are identical in structure. The difference between any two elements such as gold and mercury is in their atomic structures. They have in common, however, a relatively heavy inner core called a nucleus surrounded by one or more extremely light particles of matter called electrons. The simplest nuc
21、leus 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 protons and neutrons. A neutron is a proton combined with an electron and is electronically neutral.,Electrons whirl around nuclei in much the same manner
22、 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.2 All the elements in the universe, and therefore all matter, is composed of protons, neutrons, and electro
23、ns.There must be force of attraction between a nucleus and the electrons surrounding it, otherwise the electrons would fly off into space, in order to understand its nature, we find it helpful to call this force a charge. The charge of the nucleus is defined as positive, and the opposite charge of t
24、he electron, negative. In view of the fact that opposites attract, the force between the nucleus and the rotating electron around it prevents the electron from flying off into space.,An atom, which has all of its orbital (rotating) electrons has as many positive charges and therefore the net charge
25、is zero. When an atom loses an electron the 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 charge
26、d, such an atom is referred to as a negative ion.,Conductors, 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
27、 structures. In good conductors, 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.,Substance, which prevent the passage of electrons throug
28、h their structures are called insulators. Insulators have very few easily removed electrons in their outer rings. There are no perfect insulators: first, because of the presence of impurities (foreign materials) which can never be entirely removed; and second, because even a small amount of heat wil
29、l cause a certain number of valence electrons to be freed from their atoms.Insulators generally have very stable atomic structures, of which the 4-electron outer-ring structure is typical. In such a structure, there is an absence of easily removed electrons. Example of good insulators are certain co
30、mpounds of carbon (a basic ingredient of rubber ) and diamond, which has a similar atomic structure.,Semiconductors are a group of materials, which conduct electrons poorly and therefore cannot properly be classified either as conductors or insulators. Generally, semiconductors differ from insulator
31、s in that their outer-ring electrons can detach themselves from their orbits more easily than in insulators. Typical semiconductors materials are germanium and silicon.Impurities may be added to pure semiconductors. This results in semiconductor materials, which may either have an excess of free ele
32、ctrons 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 call the material P-type. Both N-type and P-type semiconductors are made by treated materials. such as germanium and silicon with impurities such
33、 as arsenic and indium.3 The addition of impurities to semiconductors is called doping.,KEY WORDS naturally 自然的; 天生具备 identity 标识; 标志 mercury 汞, 金属的一种 oxygen氧气; 氧元素 nucleus 原子核 proton 质子 neutrons 中子 force 力量; 力 charge 主管, 看管; 承载 orbital 眼眶; 轨道 positive 正电 negative负电,conductor 导体 semiconductor 半导体 in
34、sulator 绝缘 valence 原子价 impurity 杂质 ion 离子 excess 过剩 germanium 锗 deficiency 缺乏 arsenic 砷 indium 铟 dope 掺杂 whirl 旋转,NOTES1 Each element has a separate identify of its own, that is, no two elements have the same physical and chemical properties, nor can an element be subdivided by ordinary physical and
35、 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。,2 Electrons 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
36、 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子数和中子数。 in much the same manner that 中，inmanner意为“以的方式”，that是manner的定语从句。,3 Both N-type and P-type semiconductors are made by treated materials, su
37、ch 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 materials, treat原意为对待，treated materials指前文将杂质掺入纯净半导体的过程。,EXERCISEAfter reading the passage conclude the following sentences true or false.1. The materials that make u
38、p 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, neutrons and electrons. ( )4. When the temperature is high, an electron can attract amount heat and then fly off into space.
39、( )5. The semiconductor can permit the current through their body if some condition is supplied. ( ),6. If you put impurities adding to pure semiconductors, this results in semiconductor materials, which only have an excess of free electrons. ( )7. When an excess of electrons is present, we call the
40、 material P-type; when lack of orbitalelectrons occurs, we call the material N-type. ( )8. Both N-type and P-type semiconductors are made by treated materials. such as germanium and silicon with impurities such as arsenic and indium. ( )9. The course of addition of impurities to semiconductors is ca
41、lled doping. ( ),Passage C Diode and Transistor The Basic Crystal Junction (or Diode)When a free electron meets a moving hole in a semiconductor material, the electron occupies the free space and a positive or negative charge no longer exists; that is, the charge is neutralized. When a P-type and a
42、N-type crystal are joined to make a single semiconductor, as shown in Figure 9.1, current will flow in one direction only. As an example, when a power source is connected to the semiconductor as shown in Figure 9.2, the semiconductor is said to be forward biased.,Figure9.1 The basic crystal junction
43、,Figure9.2 Forward biased connection in,The holes will be repelled toward the junction by the positively charged battery terminal, whereas the electrons are pushed toward the junction by the batterys negative terminal.At the junction, the electrons combine with the hole. Electrons enter the semicond
44、uctor at the N terminal to replace the electrons that have combined with the holes. Likewise, electrons leave the P terminal by attraction of positive voltage and create new holes. This movement of electrons, from the negative voltage source through the junction and from the positive terminal of sem
45、iconductor to positive voltage source, creates a current flow. Thus current will flow in a semiconductor when the semiconductor is forward biased.,When the polarity of the power source is reversed, the semiconductor is said to be reverse biased. The holes are moved away from the junction by the nega
46、tive 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 current will flow.In practical terms, there will always be a few electrons and holes near the junction, allowing a very small cu
47、rrent to pass. This small current is known as leakage current and is usually in the order of a few microamperes (or possibly pico amperes).,When P-type and N-type regions are formed in same crystal, the semiconductor is known as a diode or rectifier. The boundary between the two regions is termed a
48、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 semiconductors are called diodes or signal diodes. When the device is used for conversion of alternating current (ac) to direct curre
49、nt (dc), the semiconductor is called a rectifier.,Basic Two-junction or Bipolar TransistorLike a diode, a transistor can be used to prevent (or limit) the 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, possibly, bipolar transistors. The author prefers the former term but recognizes that the latter term is also in common use.,
