專業(yè)英語5-20100407.pptVIP

專業(yè)英語-第五講,李聰 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?qū)妷?Forward bias：正偏 Multiple：倍數(shù) Reverse saturation current：反向飽和電流 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 ：關(guān)于方面的 翻譯：在正向，電流增加非常迅速，但是保持平滑的趨勢，實際上并不存在一些關(guān)于電路理論的書中提到的“正向?qū)妷骸薄?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不要直譯為強(qiáng)正偏，rather little：相當(dāng)小。注意：雖然根據(jù)文字意思，該句描述的是在較寬的電流范圍內(nèi)，電壓的變化較小，但翻譯時需結(jié)合實際物理意義。 P69，3. The Current-Voltage characteristic 翻譯：但是如圖7.6所示，在正向偏置電壓較大時，二極管上電壓的一個很小變化就會導(dǎo)致其電流發(fā)生非常大的變化。,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基本含義是“說”，還可以作為插入語，作用是“ used to suggest a possible example, amount etc when discussing something”，可翻譯為“例如”，“i.e.”拉丁語，代表“that is”. 翻譯：例如，設(shè)計一個二極管，在電壓為0.6 V (即 eV/kT = 24)時，電流為I，那么在電壓為0.427V (eV/kT= 17.1)時的電流只是0.6 V時電流的千分之一。,For practical purposes the diode is considered as off below this voltage. 提示：“below this voltage”表示“小于該電壓”，不能翻譯為“在該電壓下”，如要表達(dá)在某一電壓時的情形，應(yīng)用“on” 翻譯：從實用角度考慮，在外加電壓小于這一電壓值時，可以認(rèn)為二極管不導(dǎo)通（處于截止?fàn)顟B(tài)）。 問題：this voltage指代誰？ The difference in the on voltages of Ge and Si diodes also needs explanation. 提示：“on”voltage翻譯為“開啟電壓” 翻譯：這里也要解釋一下鍺二極管和硅二極管開啟電壓的差別。,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的定語）is the same multiple of its reverse saturation current IS. 提示：該句理解的關(guān)鍵是對“same multiple”的理解，需要對二極管的電流表達(dá)式進(jìn)行理解。此外結(jié)合實際物理意義，“its”指代的是“Ge diode ” 相關(guān)公式（P69，7.1） 翻譯：注意，如果Ge二極管外加電壓與Si二極管相同，例如均為0.7V，則流過Ge二極管的電流與其IS的比值與Si二極管的相同（流過Ge二極管和Si二極管的電流分別為各自的IS乘以相同的倍數(shù)）。,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 （插入語）- is about l08 times that of an Si diode with the same doping levels. 提示：in turn ：as a result of something，Si的本征載流子濃度ni約為1010/cm3,Ge的本征載流子濃度ni約為1014/cm3 翻譯：因為IS與少子濃度成正比，也就與(ni)2有關(guān)，因此如果Ge二極管與Si二極管的摻雜濃度相同，則Ge二極管的IS大約是Si二極管的l08倍，導(dǎo)致他們的正向電流也存在同樣的關(guān)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并列關(guān)系（肯定意思），neither對eitheror兩個內(nèi)容進(jìn)行否定 翻譯：因此Ge二極管的開啟電壓更低，典型值約為0.25V。注意，要使硅二極管能在這一電壓下導(dǎo)通，需要將其摻雜濃度縮小l08倍，或者將其結(jié)面積擴(kuò)大l08倍，實際上這都是不現(xiàn)實的。,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引導(dǎo)兩個并列的賓語從句。其中第一個賓語從句中parts of which 引導(dǎo)一個定語從句，修飾slice（書上有誤），第二個賓語從句中and連接兩個動詞不定式to extend和to allow，作狀語。 翻譯：實際上這表示器件可以采用兩種方法制備：一種方法是采用從一個大單晶錠上切割的晶片，并且從晶片表面通過擴(kuò)散或者離子注入雜質(zhì)原子使部分區(qū)域改變導(dǎo)電類型；另一種方法是采用外延技術(shù)生長一層新材料，使單晶襯底向外延伸，形成pn結(jié)。,P68課文解釋 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。 翻譯：電子能帶圖包含了關(guān)于半導(dǎo)體器件的大量信息，因此學(xué)習(xí)如何構(gòu)造不同情況的能帶圖是很值得的。,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是先行主語，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 注意與phase、step含義的區(qū)別 Phase:a part of a process of development or growth; Step: a stage in a process。 翻譯：試圖記住每種器件的能帶圖不是一個好主意，必須掌握的應(yīng)該是構(gòu)造能帶圖的簡要步驟。,(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，用動詞原形。 will不僅僅表示進(jìn)來時，還表示“used like can to show what is possible” 翻譯：。 (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基本含義是“圍繞”，還表示“at or to the other side of something”。 兩個close含義相同，第二個后面省略了 to the Fermi level。 翻譯：。,(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在專業(yè)文章中經(jīng)常出現(xiàn)，表示 to take into consideration。 第二句含義比較直觀，但是 nearer從語法關(guān)系如何理解？是一個問題。 若將nearer換成closer to就比較直觀了。 翻譯：。 (d) Complete these bands, keeping the gap between conduction and valence bands constant. 提示：現(xiàn)在分詞短語keeping修飾祈使句謂語動詞，作狀語 。 翻譯：。,(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翻譯為“雙曲線”是不對的。 curve基本含義是“曲線”，還表示a rounded bend in a road, river etc. 此處采用的是復(fù)數(shù)形式，建議翻譯為“雙彎”，。 翻譯：。 (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： 。 翻譯：。,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