专业英语5-20100407.ppt

专业英语-第五讲,李聪 2010-04-07 ,Translation,In the forward direction, the current rises very rapidly but smoothly, and there is no real forward on voltage as sometimes assumed in books on circuit theory. However, in strong forward bias, the diode voltage varies rather little over a wide current range. For example, a diode designed to carry a current I at, say, 0.6 V will carry a current of only 0.001 I at 0.427 V. For practical purposes the diode is considered as off below this voltage. The difference in the on voltages of Ge and Si diodes also needs explanation. Note that the on current for a Ge diode with the same applied voltage as an Si diode (e.g. 0.7 V) is the same multiple of its reverse saturation current IS. Since IS is proportional to the minority carrier density, which in turn depends on (ni)2, the IS of a Ge diode and hence the forward current - is about l08 times that of an Si diode with the same doping levels. Thus a Ge diode turns on at a lower voltage about 0.25 V is typical. Note that, to make an Si diode turn on at this voltage would need either a doping level about l08 times smaller, or an area l08 times bigger: neither is a practical proposition,Vocabulary,Forward on voltage：正向导通电压 Forward bias：正偏 Multiple：倍数 Reverse saturation current：反向饱和电流 Be proportional to：正比于,In the forward direction, the current rises very rapidly but smoothly, and there is no real forward on voltage as sometimes assumed in books on circuit theory. 提示：assume：to think that something is true, although you have no proof of it. books on ：关于方面的 翻译：在正向，电流增加非常迅速，但是保持平滑的趋势，实际上并不存在一些关于电路理论的书中提到的“正向导通电压”。,However, as Fig. 7.6 shows, in strong forward bias, the diode voltage varies rather little over a wide current range. 提示： strong forward bias不要直译为强正偏，rather little：相当小。注意：虽然根据文字意思，该句描述的是在较宽的电流范围内，电压的变化较小，但翻译时需结合实际物理意义。 P69，3. The Current-Voltage characteristic 翻译：但是如图7.6所示，在正向偏置电压较大时，二极管上电压的一个很小变化就会导致其电流发生非常大的变化。,For example, a diode designed to carry a current I at, say, 0.6 V (i.e. eV/kT = 24) will carry a current of only 0.001I at 0.427 V (eV/kT= 17.1) . 提示：Say基本含义是“说”，还可以作为插入语，作用是“ used to suggest a possible example, amount etc when discussing something”，可翻译为“例如”，“i.e.”拉丁语，代表“that is”. 翻译：例如，设计一个二极管，在电压为0.6 V (即 eV/kT = 24)时，电流为I，那么在电压为0.427V (eV/kT= 17.1)时的电流只是0.6 V时电流的千分之一。,For practical purposes the diode is considered as off below this voltage. 提示：“below this voltage”表示“小于该电压”，不能翻译为“在该电压下”，如要表达在某一电压时的情形，应用“on” 翻译：从实用角度考虑，在外加电压小于这一电压值时，可以认为二极管不导通（处于截止状态）。 问题：this voltage指代谁？ The difference in the on voltages of Ge and Si diodes also needs explanation. 提示：“on”voltage翻译为“开启电压” 翻译：这里也要解释一下锗二极管和硅二极管开启电压的差别。,Note that the on current for a Ge diode with the same applied voltage as an Si diode (e.g. 0.7 V) （作Ge diode的定语）is the same multiple of its reverse saturation current IS. 提示：该句理解的关键是对“same multiple”的理解，需要对二极管的电流表达式进行理解。此外结合实际物理意义，“its”指代的是“Ge diode ” 相关公式（P69，7.1） 翻译：注意，如果Ge二极管外加电压与Si二极管相同，例如均为0.7V，则流过Ge二极管的电流与其IS的比值与Si二极管的相同（流过Ge二极管和Si二极管的电流分别为各自的IS乘以相同的倍数）。,Since IS is proportional to the minority carrier density, which in turn depends on (ni)2, the IS of a Ge diode and hence the forward current （插入语）- is about l08 times that of an Si diode with the same doping levels. 提示：in turn ：as a result of something，Si的本征载流子浓度ni约为1010/cm3,Ge的本征载流子浓度ni约为1014/cm3 翻译：因为IS与少子浓度成正比，也就与(ni)2有关，因此如果Ge二极管与Si二极管的掺杂浓度相同，则Ge二极管的IS大约是Si二极管的l08倍，导致他们的正向电流也存在同样的关系。,Thus a Ge diode turns on at a lower voltage about 0.25 V is typical. Note that, to make an Si diode turn on at this voltage would need either a doping level about l08 times smaller, or an area l08 times bigger: neither is a practical proposition. 提示：eitheror并列关系（肯定意思），neither对eitheror两个内容进行否定 翻译：因此Ge二极管的开启电压更低，典型值约为0.25V。注意，要使硅二极管能在这一电压下导通，需要将其掺杂浓度缩小l08倍，或者将其结面积扩大l08倍，实际上这都是不现实的。,P-N Junction -From Wikipedia,A pn junction is formed by joining p-type and n-type semiconductors together in very close contact. The term junction refers to the boundary interface where the two regions of the semiconductor meet. If they were constructed of two separate pieces this would introduce a grain boundary, so pn junctions are created in a single crystal of semiconductor by doping, for example by ion implantation, diffusion of dopants, or by epitaxy (growing a layer of crystal doped with one type of dopant on top of a layer of crystal doped with another type of dopant). P-N junctions are elementary “building blocks“ of almost all semiconductor electronic devices such as diodes, transistors, solar cells, LEDs, and integrated circuits; they are the active sites where the electronic action of the device takes place. For example, a common type of transistor, the bipolar junction transistor, consists of two pn junctions in series, in the form npn or pnp.,In practice this means either that the device has been made from a slice cut from a large single crystal, parts of which have been transformed by diffusing or ion-implanting doping atoms from the surface, or that new material has been grown epitaxially to extend a crystal substrate and to allow the including of a pn junction. 提示：either that和or that引导两个并列的宾语从句。其中第一个宾语从句中parts of which 引导一个定语从句，修饰slice（书上有误），第二个宾语从句中and连接两个动词不定式to extend和to allow，作状语。 翻译：实际上这表示器件可以采用两种方法制备：一种方法是采用从一个大单晶锭上切割的晶片，并且从晶片表面通过扩散或者离子注入杂质原子使部分区域改变导电类型；另一种方法是采用外延技术生长一层新材料，使单晶衬底向外延伸，形成pn结。,P68课文解释 The electron-energy diagram conveys a great deal of information about a semiconductor device, and it is well worthwhile learning how to construct these diagrams. 提示：convey表示“to communicate information or a message” 例句“All this information can be conveyed in a simple diagram” to be worthwhile doing表示值得做。 翻译：电子能带图包含了关于半导体器件的大量信息，因此学习如何构造不同情况的能带图是很值得的。,It is not a good idea to try to memorize the diagram for every device-the simple stages of construction are what must be mastered. 提示： It是先行主语，代表to try ； stage表示“a particular time or state that something reaches as it grows or develops”,例句The different stages of a childs development 注意与phase、step含义的区别 Phase:a part of a process of development or growth; Step: a stage in a process。 翻译：试图记住每种器件的能带图不是一个好主意，必须掌握的应该是构造能带图的简要步骤。,(a) Start by putting the Fermi level on paper for one of the layers of semiconductor-any one will do. 提示： 是祈使句形式，用动词原形。 will不仅仅表示进来时，还表示“used like can to show what is possible” 翻译：。 (b) Build the band round this Fermi level. The conduction band is close to the Fermi level for n-type material, but the valence band is close in p-type 提示： round基本含义是“围绕”，还表示“at or to the other side of something”。 两个close含义相同，第二个后面省略了 to the Fermi level。 翻译：。,(c) Draw the other Fermi levels at the right height on the diagram, allowing for applied voltages. The more positive of two layers is nearer the bottom of the page. 提示： allowing for在专业文章中经常出现，表示 to take into consideration。 第二句含义比较直观，但是 nearer从语法关系如何理解？是一个问题。 若将nearer换成closer to就比较直观了。 翻译：。 (d) Complete these bands, keeping the gap between conduction and valence bands constant. 提示：现在分词短语keeping修饰祈使句谓语动词，作状语 。 翻译：。,(e) Join up the conduction band from each layer to the next, using S-shaped double curves, and do the same for the valence band. 提示： double curves翻译为“双曲线”是不对的。 curve基本含义是“曲线”，还表示a rounded bend in a road, river etc. 此处采用的是复数形式，建议翻译为“双弯”，。 翻译：。 (f) Fill in details such as free carriers, doping ions, and applied voltages. Remember that doping ions are present in depletion layers, but that large numbers of free carriers are not. 提示： 。 翻译：。,Breakdown voltage VB depends on the doping density of a pn junction, in particular on the doping of the more lightly doped side of the junction. Fig. 8.7 shows a plot of breakdown voltage for Si diodes of different doping. It indicates the general value of the quantities, but does not acco