運(yùn)算放大器中英文資料外文翻譯文獻(xiàn)

1、 運(yùn)算放大器中英文資料外文翻譯文獻(xiàn)運(yùn)算放大器中英文資料外文翻譯文獻(xiàn)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(yùn)算放大器中英文資料外文翻譯文獻(xiàn)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(yùn)算放大器中英文資料外文翻譯文獻(xiàn)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(yùn)算放大器中英文資料外文翻譯文獻(xiàn)A 運(yùn)算放大器對(duì)應(yīng)于像廣義放大器這樣的電子裝置，存在的一個(gè)問(wèn)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(jì)工作增加了難度。設(shè)計(jì)運(yùn)算放大器或 Op-Amp 的目的就是使它盡可能的減少對(duì)其內(nèi)部參數(shù)的依賴性、最大

22、程度地簡(jiǎn)化設(shè)計(jì)工作。運(yùn)算放大器是一個(gè)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(yùn)算放大器的全面綜合分析超越了某些教科書(shū)的范圍。在這里我們將詳細(xì)研究一個(gè)例子，然后給出兩個(gè)運(yùn)算放大器定律并說(shuō)明在許多實(shí)用電路中怎樣使用這兩個(gè)定律來(lái)進(jìn)行分析。這兩個(gè)定律可允許一個(gè)人在沒(méi)有詳細(xì)了解運(yùn)算放大器物理特性的情況下設(shè)計(jì)各種電路。因此，運(yùn)算放大器對(duì)于在不同技術(shù)領(lǐng)域中需要使用簡(jiǎn)單放大器而不是在晶體管級(jí)做設(shè)計(jì)的研究人員來(lái)說(shuō)是非常有用的。在電路和電子學(xué)教科書(shū)中，也說(shuō)明了如何用運(yùn)算放大器建立簡(jiǎn)單的濾波電路。作為構(gòu)建運(yùn)算放大器集成電路的積木晶體管，將在下篇課文中進(jìn)行討論。 運(yùn)算

23、放大器中英文資料外文翻譯文獻(xiàn)理想運(yùn)算放大器的符號(hào)如圖 1-2A-1 所示。圖中只給出三個(gè)管腳：正輸入、負(fù)輸入和輸出。讓運(yùn)算放大器正常運(yùn)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(huà)出。在實(shí)際電路中使用運(yùn)算放大器時(shí)，后者是必要的，但在本文中討論理想的運(yùn)算放大器的應(yīng)用時(shí)則不必考慮后者。兩個(gè)輸入電壓和輸出電壓用符號(hào)U、U和U 表示。每一個(gè)電壓均指的是相對(duì)于接零管腳的電位。運(yùn)算放大器是差分裝置。差分的意思是：相對(duì)于接零管腳的輸出電壓可由下式表示式中 A 是運(yùn)算放大器的增益，U 和 U 是輸入電壓。換句話說(shuō)，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(yùn)算放大器成功的一個(gè)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(shuō)，等式(1-2A-1)中的數(shù) A 約為 100,000 或更多(例如，五個(gè)晶體管放大器串聯(lián)，每一個(gè)的增益為 10，那么將會(huì)得到此數(shù)值的 A)。第二個(gè)重要因素是這些電路是按照流入每一個(gè)輸入的電流都很小這樣的原則來(lái)設(shè)計(jì)制作的。第三個(gè)重要的設(shè)計(jì)特點(diǎn)就是運(yùn)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(gè)電流定義如圖1-2A-2 中的 b 圖所示。對(duì)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?yàn)檫\(yùn)算放大器是按照沒(méi)有電流流入正輸入端和負(fù)輸入端的原則制作的，即(1-2A-3) 運(yùn)算放大器中英文資料外文翻譯文獻(xiàn)根據(jù)電流參考方向和接零管腳電位為零伏特的事實(shí)，利用歐姆定律，可得負(fù)因此 U =IR ，并由式 (1-2A-3)可得：-因?yàn)楝F(xiàn)在已有了 U 和 U 的表達(dá)式，所以式(1-2A-1)可用于計(jì)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(gè)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(xiàng)決定，存在于分子和分母的系數(shù) A 就可對(duì)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(wú)關(guān)并能夠通過(guò) R 和R 的選擇來(lái)2控制。這是運(yùn)算放大器設(shè)計(jì)的重要特征之-在信號(hào)作用下，電路的動(dòng)作僅取決于能夠容易被設(shè)計(jì)者改變的外部元件，而不取決于運(yùn)算放大器本身的細(xì)節(jié)特性。注意，如果 A=100,000， 而(R +R) /R =10，那么為此優(yōu)點(diǎn)而付出的代價(jià)是用一個(gè)具有 100,000 倍電壓增益的器件產(chǎn)生一個(gè)具有 10 倍增益的放大器。從某種意義上說(shuō)，使用運(yùn)算放大器是以“能量”為代價(jià)來(lái)?yè)Q取“控制”。對(duì)各種運(yùn)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(yùn)算放大器兩個(gè)定律應(yīng)用。1) 第一個(gè)定律指出：在一般運(yùn)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(shuō)，U =U2) 第二個(gè)定律指出：在一般運(yùn)算放大器電路中，兩個(gè)輸入電流可被假定為I =I =0第一個(gè)定律是因?yàn)閮?nèi)在增益 A 的值很大。例，如果運(yùn)算放大器的輸出是 1V，并且 A=100,000, 那么(U = U )=10 V 這是一個(gè)非常小、可以忽略的數(shù)，因此可設(shè)U = U 。第二個(gè)定律來(lái)自于運(yùn)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(méi)有+ -電流流入任何一個(gè)輸入端。 運(yùn)算放大器中英文資料外文翻

28、譯文獻(xiàn)B 晶體管簡(jiǎn)單地說(shuō)，半導(dǎo)體是這樣一種物質(zhì)，它能夠通過(guò)“摻雜”來(lái)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(guò)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(gè)二極管，公共中間層是以對(duì)等的方式向兩個(gè)邊緣層滲入而得，因此中間層比兩個(gè)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(gè)基本類型。因?yàn)榫w管包含兩個(gè)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(gè)晶體管有三個(gè)區(qū)域，并從這三個(gè)區(qū)域引出三個(gè)管腳。要使工作電路運(yùn)行，晶體管需與兩個(gè)外部電壓或極性連接。其中一個(gè)外部電壓工作方式類似于二極管。事實(shí)上，保留這個(gè)外部電壓并去掉上半部分，晶體管將會(huì)象二極管一樣工作。例如在簡(jiǎn)易收音機(jī)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(gè)電壓被加到晶體管的頂部和底部?jī)蓚€(gè)極之間，并且底部電壓極性相同，那么，流過(guò)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(guò)的電流。在生產(chǎn)晶體管的過(guò)程中，通過(guò)控制不同層的摻雜度，經(jīng)過(guò)負(fù)載電阻流過(guò)第二個(gè)電路電流的導(dǎo)電能力非常顯著。實(shí)際上，當(dāng)晶體管下半部為正向偏置時(shí)，底部的 P 區(qū)就像一個(gè)取之不竭的自由電子源（因?yàn)榈撞康?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(guò)這個(gè)特定電路實(shí)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(shí)，實(shí)際上存在兩個(gè)獨(dú)立的“工作”電路。一個(gè)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(gè)是由集電極電壓源和晶體管的三個(gè)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(yùn)算放大器中英文資料外文翻譯文獻(xiàn)個(gè)電路的公共端時(shí)-被稱為共發(fā)射極連接。）這是晶體管最常見(jiàn)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(diǎn)是相對(duì)小的基極電流能控制和激發(fā)出一個(gè)比它大得多的集電極電流(或更恰當(dāng)?shù)卣f(shuō)，一個(gè)小的輸入功率能夠產(chǎn)生一個(gè)比它大得多的輸出功率)。換句話說(shuō)，晶體管的作用相當(dāng)于一個(gè)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(guò)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(gè)電路實(shí)際上是獨(dú)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(gè)反向偏置二極管，因此沒(méi)