运算放大器中英文资料外文翻译文献

1、 运算放大器中英文资料外文翻译文献运算放大器中英文资料外文翻译文献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) 运算放大器中英文资料外文翻译文献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. 运算放大器中英文资料外文翻译文献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. 运算放大器中英文资料外文翻译文献A 运算放大器对应于像广义放大器这样的电子装置，存在的一个问题就是它们的增益 AU或 A 它们取决于双端口系统(、R 、R 等)的内部特性。器件之间参数的分I,i0散性和温度漂移给设计工作增加了难度。设计运算放大器或 Op-Amp 的目的就是使它尽可能的减少对其内部参数的依赖性、最大

22、程度地简化设计工作。运算放大器是一个集成电路，在它内部有许多电阻、晶体管等元件。就此而言，我们不再描述这些元件的内部工作原理。运算放大器的全面综合分析超越了某些教科书的范围。在这里我们将详细研究一个例子，然后给出两个运算放大器定律并说明在许多实用电路中怎样使用这两个定律来进行分析。这两个定律可允许一个人在没有详细了解运算放大器物理特性的情况下设计各种电路。因此，运算放大器对于在不同技术领域中需要使用简单放大器而不是在晶体管级做设计的研究人员来说是非常有用的。在电路和电子学教科书中，也说明了如何用运算放大器建立简单的滤波电路。作为构建运算放大器集成电路的积木晶体管，将在下篇课文中进行讨论。 运算

23、放大器中英文资料外文翻译文献理想运算放大器的符号如图 1-2A-1 所示。图中只给出三个管脚：正输入、负输入和输出。让运算放大器正常运行所必需的其它一些管脚，诸如电源管脚、接零管脚等并未画出。在实际电路中使用运算放大器时，后者是必要的，但在本文中讨论理想的运算放大器的应用时则不必考虑后者。两个输入电压和输出电压用符号U、U和U 表示。每一个电压均指的是相对于接零管脚的电位。运算放大器是差分装置。差分的意思是：相对于接零管脚的输出电压可由下式表示式中 A 是运算放大器的增益，U 和 U 是输入电压。换句话说，输出电压是-A 乘以两输入间的电位差。集成电路技术使得在非常小的一块半导体材料的复合 “

24、芯片”上可以安装许多放大器电路。运算放大器成功的一个关键就是许多晶体管放大器“串联”以产生非常大的整体增益。也就是说，等式(1-2A-1)中的数 A 约为 100,000 或更多(例如，五个晶体管放大器串联，每一个的增益为 10，那么将会得到此数值的 A)。第二个重要因素是这些电路是按照流入每一个输入的电流都很小这样的原则来设计制作的。第三个重要的设计特点就是运算放大器的输出阻抗(R )非常小。也0我们现在利用这些特性就可以分析图 1-2A-2 所示的特殊放大器电路了。首先，注意到在正极输入的电压 U 等于电源电压，即 U =U 。各个电流定义如图1-2A-2 中的 b 图所示。对图 1-2A

25、-2b 的外回路应用基尔霍夫定律，注意输出电压U 指的是它与接零管脚之间的电位，我们就可得到0因为运算放大器是按照没有电流流入正输入端和负输入端的原则制作的，即(1-2A-3) 运算放大器中英文资料外文翻译文献根据电流参考方向和接零管脚电位为零伏特的事实，利用欧姆定律，可得负因此 U =IR ，并由式 (1-2A-3)可得：-因为现在已有了 U 和 U 的表达式，所以式(1-2A-1)可用于计算输出电压，-综合上述等式，可得： U =1+AR /(R +R )= AU2A = U/U= A(R +R )/( R +R+AR)1这是电路的增益系数。如果 A 是一个非常大的数，大到足够使 AR (

26、R +R )，2那么分式的分母主要由 AR 项决定，存在于分子和分母的系数 A 就可对消，增益1可用下式表示这表明，(1-2A-5b)如果A 非常大，那么电路的增益与 A 的精确值无关并能够通过 R 和R 的选择来2控制。这是运算放大器设计的重要特征之-在信号作用下，电路的动作仅取决于能够容易被设计者改变的外部元件，而不取决于运算放大器本身的细节特性。注意，如果 A=100,000， 而(R +R) /R =10，那么为此优点而付出的代价是用一个具有 100,000 倍电压增益的器件产生一个具有 10 倍增益的放大器。从某种意义上说，使用运算放大器是以“能量”为代价来换取“控制”。对各种运算放

27、大器电路都可作类似的数学分析，但是这比较麻烦，并且存在一些非常有用的捷径，其涉及目前我们提出的运算放大器两个定律应用。1) 第一个定律指出：在一般运算放大器电路中，可以假设输入 端间的电压为零，也就是说，U =U2) 第二个定律指出：在一般运算放大器电路中，两个输入电流可被假定为I =I =0第一个定律是因为内在增益 A 的值很大。例，如果运算放大器的输出是 1V，并且 A=100,000, 那么(U = U )=10 V 这是一个非常小、可以忽略的数，因此可设U = U 。第二个定律来自于运算放大器的内部电路结构，此结构使得基本上没有+ -电流流入任何一个输入端。 运算放大器中英文资料外文翻

28、译文献B 晶体管简单地说，半导体是这样一种物质，它能够通过“掺杂”来产生多余的电子，又称自由电子（N 型）；或者产生“空穴”，又称正电荷（P 型）。由 N 型掺杂和 P 型掺杂处理的锗或硅的单晶体可形成半导体二极管，它具有我们描述过的工作特性。晶体管以类似的方式形成，就象带有公共中间层、背靠背的两个二极管，公共中间层是以对等的方式向两个边缘层渗入而得，因此中间层比两个边缘层或边缘区要薄的多。PNP 或 NPN (图 1-2B-1)这两种结构显然是可能的。PNP 或 NPN 被用于描述晶体管的两个基本类型。因为晶体管包含两个不同极性的区域（例如“P”区和“N”区），所以晶体管被叫作双向器件，或双

29、向晶体管。一个晶体管有三个区域，并从这三个区域引出三个管脚。要使工作电路运行，晶体管需与两个外部电压或极性连接。其中一个外部电压工作方式类似于二极管。事实上，保留这个外部电压并去掉上半部分，晶体管将会象二极管一样工作。例如在简易收音机中用晶体管代替二极管作为检波器。在这种情况下，其所起的作用和二极管所起的作用一模一样。可以给二极管电路加正向偏置电压或反向偏置电压。在加正向偏置电压的情况下，如图 1-2B-2 所示的 PNP 晶体管，电流从底部的 P 极流到中间的 N 极。如果第二个电压被加到晶体管的顶部和底部两个极之间，并且底部电压极性相同，那么，流过中间层 N 区的电子将激发出从晶体管底部到

30、顶部流过的电流。在生产晶体管的过程中，通过控制不同层的掺杂度，经过负载电阻流过第二个电路电流的导电能力非常显著。实际上，当晶体管下半部为正向偏置时，底部的 P 区就像一个取之不竭的自由电子源（因为底部的 P 区发射电子，所以它被称为发射极）。这些电子被顶部 P 区接收，因此它被称为集电极，但是流过这个特定电路实际电流的大小由加到中间层的偏置电压控制，所以中间层被称为基极。因此，当晶体管外加电压接连正确（图 1-2B-3）后工作时，实际上存在两个独立的“工作”电路。一个是由偏置电压源、发射极和基极形成的回路，它被称为基极电路或输入电路；第二个是由集电极电压源和晶体管的三个区共同形成的电路，它被称

31、为集电极电路或输出电路。（注意：本定义仅适用于发射极是两 运算放大器中英文资料外文翻译文献个电路的公共端时-被称为共发射极连接。）这是晶体管最常见的连接方式，但是，当然也存在其它两种连接方法-共基极连接和共集电极连接。但是，在每一种情况下晶体管的工作原理是相同的。本电路的突出优点是相对小的基极电流能控制和激发出一个比它大得多的集电极电流(或更恰当地说，一个小的输入功率能够产生一个比它大得多的输出功率)。换句话说，晶体管的作用相当于一个放大器。在这种工作方式中，基极-发射极电路是输入侧；通过基极的发射极和集电极电路是输出侧。虽然基极和发射极是公共路径，但这两个电路实际上是独立的，就基极电路的极性而言，基极和晶体管的集电极之间相当于一个反向偏置二极管，因此没