運算放大器中英文資料外文翻譯文獻

1、 運算放大器中英文資料外文翻譯文獻運算放大器中英文資料外文翻譯文獻A: The Operational AmplifierOne problem with electronic devices corresponding to the generalized amplifiers is thatthe gains, Au or A, depend upon internal properties of the two-port system (p, fl, R, Ro, etc.)?This makes design difficult since these parameters usual

2、ly vary from device to device, as well aswith temperature. The operational amplifier, or Op-Amp, is designed to minimize thisdependence and to maximize the ease of design. An Op-Amp is an integrated circuit that hasmany component part such as resistors and transistors built into the device. At this

3、point we willmake no attempt to describe these inner workings.A totally general analysis of the Op-Amp is beyond the scope of some texts. We willinstead study one example in detail, then present the two Op-Amp laws and show how they canbe used for analysis in many practical circuit applications. The

4、se two principles allow one todesign many circuits without a detailed understanding of the device physics. Hence, Op-Amps arequite useful for researchers in a variety of technical fields who need to build simple amplifiers butdo not want to design at the transistor level. In the texts of electrical

5、circuits and electronics theywill also show how to build simple filter circuits using Op-Amps. The transistor amplifiers, whichare the building blocks from which Op-Amp integrated circuits are constructed, will be discussed.The symbol used for an ideal Op-Amp is shown in Fig. 1-2A-1. Only three conn

6、ections are at the two inputs and the output will beUo =A(U+ -U-)(1-2A-l)(1-2A-2)1120 -Using Eq. (1-2A-2) and settingI =I =I,12(1-2A-3)01So,and from Eq. (1-2A-3),0Since we now have expressions for U+ and U-, Eq. (1-2A-l) may be used to calculate the outputvoltage,U =1+AR /(R +R )= AU2(1-2A-4)A = U/U

7、= A(R +R )/( R+R +AR )1(1-2A-5a)(1-2A-5b) 運算放大器中英文資料外文翻譯文獻easily varied by the designer and which do not depend upon the detailed character of theOp-Amp itself. Note that if A=100 000 and (R1 +R2)/R1=10, the price we have paid for thisadvantage is that we have used a device with a voltage gain of 10

8、0 000 to produce an amplifierwith a gain of 10. In some sense, by using an Op-Amp we trade off power for control.A similar mathematical analysis can be made on any Op-Amp circuit, but this iscumbersome and there are some very useful shortcuts that involve application of the two laws ofOp-Amps which

9、we now present.1) The first law states that in normal Op-Amp circuits we may assume that the voltagedifference between the input terminals is zero, that is,U =U+-2) The second law states that in normal Op-Amp circuits both of the input currents may beassumed to be zero:I =I =0+ -The first law is due

10、 to the large value of the intrinsic gain A. For example, if the output of an Op-Amp is IV and A= 100 000, then ( U+ - U- )= 10-SV. This is such a small number that it can often beignored, and we set U+ = U-. The second law comes from the construction of the circuitry insidethe Op-Amp which is such

11、that almost no current flows into either of the two inputs.B: TransistorsPut very simply a semiconductor material is one which can be doped to produce apredominance of electrons or mobile negative charges (N-type); or holes or positive charges (P-type). A single crystal of germanium or silicon treat

12、ed with both N-type dope and P-type dopeforms a semiconductor diode, with the working characteristics described. Transistors are formedin a similar way but like two diodes back-to-back with a common middle layer doped in theopposite way to the two end layers, thus the middle layer is much thinner th

13、an the two endlayers or zones.Two configurations are obviously possible, PNP or NPN (Fig. 1-2B-l). These descriptions areused to describe the two basic types of transistors. Because a transistor contains elements withtwo different polarities (i.e., P and N zones), it is referred to as a bipolar devi

14、ce, or bipolar transistor.aflow of current through the transistor bottom-to-top. relative to base and collector (N for negative in the caseof an NPN transistor). This is also inferred by the reverse direction of the arrow on the emitter inthe symbol for an NPN transistor, i.e., current flow away fro

15、m the base. 運算放大器中英文資料外文翻譯文獻While transistors are made in thousands of different types, the number of shapes in whichthey are produced is more limited and more or less standardized in a simple code - TO (TransistorOutline) followed by a number.TO1 is the original transistor shape a cylindrical can w

16、ith the three leads emerging intriangular pattern from the bottom. Looking at the base, the upper lead in the triangle is thebase, the one to the fight (marked by a color spot) the collector and the one to the left theemitter.2 The collector lead may also be more widely spaced from the base lead tha

17、n theemitter lead.In other TO shapes the three leads may emerge in similar triangular pattern (but notnecessarily with the same positions for base, collector and emitter), or in-line. Just to confuse theissue there are also sub-types of the same TO number shape with different lead designations. TheT

18、O92, for example, has three leads emerging in line parallel to a flat side on an otherwise circularcan reading 1,2,3 from top to bottom with the flat side to the right looking at the base.With TO92 sub-type a (TO92a): 1=emitter2=collector3=baseWith TO92 sub-type b (TO92b): 1=emitter2=base3=collector

19、To complicate things further, some transistors may have only two emerging leads (the thirdbeing connected to the case internally); and some transistor outline shapes are found with morethan three leads emerging from the base. These, in fact, are integrated circuits (ICs), packaged inthe same outline

20、 shape as a transistor. More complex ICs are packaged in quite different form,e.g., flat packages.Power transistors are easily identified by shape They are metal cased with an elongatedbottom with two mounting holes. There will only be two leads (the emitter and base) and thesewill normally be marke

21、d. The collector is connected internally to the can, and so connection tothe collector is via one of the mounting bolts or bottom of the can. 運算放大器中英文資料外文翻譯文獻A 運算放大器對應(yīng)于像廣義放大器這樣的電子裝置，存在的一個問題就是它們的增益 AU或 A 它們?nèi)Q于雙端口系統(tǒng)(、R 、R 等)的內(nèi)部特性。器件之間參數(shù)的分I,i0散性和溫度漂移給設(shè)計工作增加了難度。設(shè)計運算放大器或 Op-Amp 的目的就是使它盡可能的減少對其內(nèi)部參數(shù)的依賴性、最大

22、程度地簡化設(shè)計工作。運算放大器是一個集成電路，在它內(nèi)部有許多電阻、晶體管等元件。就此而言，我們不再描述這些元件的內(nèi)部工作原理。運算放大器的全面綜合分析超越了某些教科書的范圍。在這里我們將詳細研究一個例子，然后給出兩個運算放大器定律并說明在許多實用電路中怎樣使用這兩個定律來進行分析。這兩個定律可允許一個人在沒有詳細了解運算放大器物理特性的情況下設(shè)計各種電路。因此，運算放大器對于在不同技術(shù)領(lǐng)域中需要使用簡單放大器而不是在晶體管級做設(shè)計的研究人員來說是非常有用的。在電路和電子學(xué)教科書中，也說明了如何用運算放大器建立簡單的濾波電路。作為構(gòu)建運算放大器集成電路的積木晶體管，將在下篇課文中進行討論。 運算

23、放大器中英文資料外文翻譯文獻理想運算放大器的符號如圖 1-2A-1 所示。圖中只給出三個管腳：正輸入、負輸入和輸出。讓運算放大器正常運行所必需的其它一些管腳，諸如電源管腳、接零管腳等并未畫出。在實際電路中使用運算放大器時，后者是必要的，但在本文中討論理想的運算放大器的應(yīng)用時則不必考慮后者。兩個輸入電壓和輸出電壓用符號U、U和U 表示。每一個電壓均指的是相對于接零管腳的電位。運算放大器是差分裝置。差分的意思是：相對于接零管腳的輸出電壓可由下式表示式中 A 是運算放大器的增益，U 和 U 是輸入電壓。換句話說，輸出電壓是-A 乘以兩輸入間的電位差。集成電路技術(shù)使得在非常小的一塊半導(dǎo)體材料的復(fù)合 “

24、芯片”上可以安裝許多放大器電路。運算放大器成功的一個關(guān)鍵就是許多晶體管放大器“串聯(lián)”以產(chǎn)生非常大的整體增益。也就是說，等式(1-2A-1)中的數(shù) A 約為 100,000 或更多(例如，五個晶體管放大器串聯(lián)，每一個的增益為 10，那么將會得到此數(shù)值的 A)。第二個重要因素是這些電路是按照流入每一個輸入的電流都很小這樣的原則來設(shè)計制作的。第三個重要的設(shè)計特點就是運算放大器的輸出阻抗(R )非常小。也0我們現(xiàn)在利用這些特性就可以分析圖 1-2A-2 所示的特殊放大器電路了。首先，注意到在正極輸入的電壓 U 等于電源電壓，即 U =U 。各個電流定義如圖1-2A-2 中的 b 圖所示。對圖 1-2A

25、-2b 的外回路應(yīng)用基爾霍夫定律，注意輸出電壓U 指的是它與接零管腳之間的電位，我們就可得到0因為運算放大器是按照沒有電流流入正輸入端和負輸入端的原則制作的，即(1-2A-3) 運算放大器中英文資料外文翻譯文獻根據(jù)電流參考方向和接零管腳電位為零伏特的事實，利用歐姆定律，可得負因此 U =IR ，并由式 (1-2A-3)可得：-因為現(xiàn)在已有了 U 和 U 的表達式，所以式(1-2A-1)可用于計算輸出電壓，-綜合上述等式，可得： U =1+AR /(R +R )= AU2A = U/U= A(R +R )/( R +R+AR)1這是電路的增益系數(shù)。如果 A 是一個非常大的數(shù)，大到足夠使 AR (

26、R +R )，2那么分式的分母主要由 AR 項決定，存在于分子和分母的系數(shù) A 就可對消，增益1可用下式表示這表明，(1-2A-5b)如果A 非常大，那么電路的增益與 A 的精確值無關(guān)并能夠通過 R 和R 的選擇來2控制。這是運算放大器設(shè)計的重要特征之-在信號作用下，電路的動作僅取決于能夠容易被設(shè)計者改變的外部元件，而不取決于運算放大器本身的細節(jié)特性。注意，如果 A=100,000， 而(R +R) /R =10，那么為此優(yōu)點而付出的代價是用一個具有 100,000 倍電壓增益的器件產(chǎn)生一個具有 10 倍增益的放大器。從某種意義上說，使用運算放大器是以“能量”為代價來換取“控制”。對各種運算放

27、大器電路都可作類似的數(shù)學(xué)分析，但是這比較麻煩，并且存在一些非常有用的捷徑，其涉及目前我們提出的運算放大器兩個定律應(yīng)用。1) 第一個定律指出：在一般運算放大器電路中，可以假設(shè)輸入 端間的電壓為零，也就是說，U =U2) 第二個定律指出：在一般運算放大器電路中，兩個輸入電流可被假定為I =I =0第一個定律是因為內(nèi)在增益 A 的值很大。例，如果運算放大器的輸出是 1V，并且 A=100,000, 那么(U = U )=10 V 這是一個非常小、可以忽略的數(shù)，因此可設(shè)U = U 。第二個定律來自于運算放大器的內(nèi)部電路結(jié)構(gòu)，此結(jié)構(gòu)使得基本上沒有+ -電流流入任何一個輸入端。 運算放大器中英文資料外文翻

28、譯文獻B 晶體管簡單地說，半導(dǎo)體是這樣一種物質(zhì)，它能夠通過“摻雜”來產(chǎn)生多余的電子，又稱自由電子（N 型）；或者產(chǎn)生“空穴”，又稱正電荷（P 型）。由 N 型摻雜和 P 型摻雜處理的鍺或硅的單晶體可形成半導(dǎo)體二極管，它具有我們描述過的工作特性。晶體管以類似的方式形成，就象帶有公共中間層、背靠背的兩個二極管，公共中間層是以對等的方式向兩個邊緣層滲入而得，因此中間層比兩個邊緣層或邊緣區(qū)要薄的多。PNP 或 NPN (圖 1-2B-1)這兩種結(jié)構(gòu)顯然是可能的。PNP 或 NPN 被用于描述晶體管的兩個基本類型。因為晶體管包含兩個不同極性的區(qū)域（例如“P”區(qū)和“N”區(qū)），所以晶體管被叫作雙向器件，或雙

29、向晶體管。一個晶體管有三個區(qū)域，并從這三個區(qū)域引出三個管腳。要使工作電路運行，晶體管需與兩個外部電壓或極性連接。其中一個外部電壓工作方式類似于二極管。事實上，保留這個外部電壓并去掉上半部分，晶體管將會象二極管一樣工作。例如在簡易收音機中用晶體管代替二極管作為檢波器。在這種情況下，其所起的作用和二極管所起的作用一模一樣?？梢越o二極管電路加正向偏置電壓或反向偏置電壓。在加正向偏置電壓的情況下，如圖 1-2B-2 所示的 PNP 晶體管，電流從底部的 P 極流到中間的 N 極。如果第二個電壓被加到晶體管的頂部和底部兩個極之間，并且底部電壓極性相同，那么，流過中間層 N 區(qū)的電子將激發(fā)出從晶體管底部到

30、頂部流過的電流。在生產(chǎn)晶體管的過程中，通過控制不同層的摻雜度，經(jīng)過負載電阻流過第二個電路電流的導(dǎo)電能力非常顯著。實際上，當(dāng)晶體管下半部為正向偏置時，底部的 P 區(qū)就像一個取之不竭的自由電子源（因為底部的 P 區(qū)發(fā)射電子，所以它被稱為發(fā)射極）。這些電子被頂部 P 區(qū)接收，因此它被稱為集電極，但是流過這個特定電路實際電流的大小由加到中間層的偏置電壓控制，所以中間層被稱為基極。因此，當(dāng)晶體管外加電壓接連正確（圖 1-2B-3）后工作時，實際上存在兩個獨立的“工作”電路。一個是由偏置電壓源、發(fā)射極和基極形成的回路，它被稱為基極電路或輸入電路；第二個是由集電極電壓源和晶體管的三個區(qū)共同形成的電路，它被稱

31、為集電極電路或輸出電路。（注意：本定義僅適用于發(fā)射極是兩 運算放大器中英文資料外文翻譯文獻個電路的公共端時-被稱為共發(fā)射極連接。）這是晶體管最常見的連接方式，但是，當(dāng)然也存在其它兩種連接方法-共基極連接和共集電極連接。但是，在每一種情況下晶體管的工作原理是相同的。本電路的突出優(yōu)點是相對小的基極電流能控制和激發(fā)出一個比它大得多的集電極電流(或更恰當(dāng)?shù)卣f，一個小的輸入功率能夠產(chǎn)生一個比它大得多的輸出功率)。換句話說，晶體管的作用相當(dāng)于一個放大器。在這種工作方式中，基極-發(fā)射極電路是輸入側(cè)；通過基極的發(fā)射極和集電極電路是輸出側(cè)。雖然基極和發(fā)射極是公共路徑，但這兩個電路實際上是獨立的，就基極電路的極性而言，基極和晶體管的集電極之間相當(dāng)于一個反向偏置二極管，因此沒