电子电路数字模拟外文翻译外文文献英文文献电子电路数字与模拟下册.doc

1外文译文节选自 （美）c.a.霍尔特 电子电路 数字与模拟 下册1 .1基本放大器研究放大器，我们首先分析图1.1的电路，它包含一个偏置于放大区的npn晶体管。虽然基区宽度w是集电极电压的函数，但为了使讨论尽可能简化，将忽略这个次要的效应。因此，ies和af看作常数。符号在这里以及整个这本书中，采用标准符号表示电流和电压。电流为ib 为ib=ib+ib 图 1.1当vi为零时，图1.1 的电路叫做静态，即处于休止状态，静态基极电流为ib；当vi不为零时，总电流ib与静态值之差为ib。 符号ib表示增量电流，也称为ib的信号分量。注意：ib ，ib ，ib的习惯参考方向均以流入器件的b端为正。vbe表示从基极b到发射极e的电压降，同样把它写成静态电压vbe和增量电压vbe之和。图121电路中vbe就是vi。总之，小写字母带大写下标表示各总电流和总电压；大写字母带大写下标表示各静态量；小写字母带小写下标用于各增量变量。不特别声明，电流参考方向均以流入器件为正。电压参考方向用双下标，或象图2.1中vo那样用正负符号表示时，则q点的电压和电流均指静态量。图1.12 运算放大器除前一章讨论过的共射、共集和共基电路以外，还有另一种特别重要的基本组态，这就是差分放大器。它有两个信号电压输入瑞和一个正比于输入信号差值的输出端。常常，从提供负反馈的分压网络上提取输出的一部分作为一个输入电压；而有时，一个输入端甘脆接地。在这两种情况下，差分放大器都变成只有一个输入和一个输出的单端放大器。我们将看到，差分放大器可以处理较大的信号而没有过大的非线性失真，而且这个较大的动态范围是它的众多特性之一。由于偏流不大时输入阻抗为中到高阻抗，所以信号源负载不会过重。在低频工作(包括直流)是可能的。其电路结构特别适合子集成电路制造，因而多数线性集成电路包含一级或多级差分放大器。这类电路的实例有：模拟计算机网络、单片稳压器、视频放大器、模拟比较器和运算放大器。在本章和后续几聋中把运算放大2e的多功能性和通用性作重点是正确的。运算放大器是具有差分输入级的多级结构，其特征为电压增益大、输入阻抗高和输出阻抗低。它广泛用于许多不同类型的线性和非线性电路中。应用涉及到仪表电路、特殊用途的线性放大器、振荡器、有服滤波器及其他电路。事实上，凡是要求廉价电压放大的场合，都应考虑采用运算放大器。本章研究运算放大器的一些基本特性，若干应用也包括在内。其他问题则将在后续几章中提出。在15章和17章中示出并扼要讨论三种不同的运算放大器的电路，让我们从差分放大器开始学起。2.1 差分放大器射极耦合放大器有各种类型的差分放大器。常见的电路结构是把两个bjt的发射极安排成增量串联。实例示于图2.1.1。在该电路中理想电流源提供恒定的直流电流idc。因此，对发射极电流的增量成分理想电流源为开路。其增量电路具有图141b的形式。图中，理想的直流电压源及电流源已分别用短路和开路代换。显然ie1-ie2。就增量电流而言放大器的两个发射极相串联(如图2.1.2的两个发射极那样)，称为射极耦合放大器。重要的是晶体管q1和q2要尽可能配对，使它们的特性近于一致。当晶体管配对和输入电压为零时，两个晶体管的集电极电流就相同。从电路对称性来看这是明显的。即使省略ql的集电级电阻，两个电流也差不多相等，因为工作于放大区的bjt的集电极电流与vce几乎无关。于是，该电阻有时被省略。保留它的目的在于改善直流平衡。在增量模型中，与高阻抗集电极(其作用宛如电流源)相串联的电阻没有什么影响。输入端a和b是q1和q2的基极端。增量模型对于小信号是线性的，可应用迭加原理。因此，对两个输入我们可以分别处理。令vs20，对这种情况,增量电路可画成两极放大器的形式，图2.1.1 完整电路图2.1.2 增量模型图2.1.3 增量模型 如图2.1.2所示。正如前面指出过的，第一级rc的影响可以忽略。可见这级近似为共集组态，而第二级则为共基。该级联的输入阻抗是具有相同rs和rx值的共射放大器输入阻抗的两倍。只要负载电阻小于ro，在共集和共基两种放大器中在正向传输时可忽赂电阻r和ro。以共基级低输入阻抗作负载的共集级显然满足这个要求。因为负载电阻rc通常比实际电路中的ro小得多，所以共基极也满足这个要求。当vs10，加入vs2时，情况是相似的。输出电压则可从任一集电极取得。事实上，我们将看到，两个集电极电阻上的增量电压幅度相等而符号相反。因此，以下分析将忽略与基区宽度调制有关的参数。当信号源电阻rs加到电路时，中间频段的增量模型如图 2.1.3所示。假定两只晶体管是配对的，并有同样的静态点和增量参数。每个集电极电阻rc与集电极增量电流源相串联。因此，这些电阻不影响电路的电流。进一步说，如果去掉一个电阻，不改变另电阻上的电压。在发射极节点的节点方程表明ili2。显然，两个输出电压幅度相等而符号相反。差模电压增益与共模电压增益由图2.1.4外电路的回路方程求得 （2.1.1）输出电压voorci2，差模电压增益ad定义为输出电压与两个输入电压之差的比，即 （2.1.2） 图 2.1.4 模型之间的频带 输出vo是vo的负值。据165节中的讨论，这种放大器可用作分相器。每个输出都正比于两个输入之差vs1vs2。该差值叫做差模输入电压vd，即两个输入电压的平均值是1/2(vs1+vs2)，代表共模输入电压vc,因此当两个输入电压被此相等时输出电压与共模输入电压之比是共模增益ac对于图 2.1.3的电路，当两个输入电压相等时输出电压为零，因而共模增益为零。只要应用图 2.1.3的简化模型，即使两只晶体管不配对，共模增益也为零。对这种情况，由节点方程可证明电流：i1和i2彼此成正比，因而当两个输入电压相等时两个电流必然为零。然而，如果计入基区宽度调制电阻ro和r，容易证明对未配对的晶体管，通常ac不为零。因此，尽管这些电阻对差模增益的影响可忽略，在计算ac时，模型中应当包括ro和r。图2.1.3的模型并没有包括提供静态发射极电流的实际电源的增量电阻。这个电阻通常很大，在确定差模增益时可把它忽略。但在确定ac时，它可能是重要的。甚至对于配对的晶体管，这个电阻在模型中出现时，都会使ac不为零。在低频时，ac值可正可负。因为要求输出正比于两个输入之差，所以当两个输入相等时输出应当极小。理想时ac应为零。一个重要的品质因数是共模抑制比(cmrr)。 使用完全对称的电路，采用配对的晶体管和具有很高增量电阻的直流电流源，可以获得较大的cmrr值。通常，cmrr由实验求得，其值可能大于105或100 db。由已勿的cmrr和ad值，可求出共模增益ac的大小，但不能确定其正负。2.2 有源rc滤波器滤波器允许一个或不止一个传输频带，同时阻断这些频带以外的信号。在低通滤波器中，传输频带从零延伸到某个最高频率。高通滤波器只通过高于某个规定值的频率。还有带通滤波器和带阻滤波器。陷波滤波器滤掉一个很窄的频带，有时把它放在放大器的反馈网络中以获得窄带带通滤波器。无源滤波器由电阻、电容、电感组成，而有源rc滤波器由电阻、电容和有源器件组成。去掉电感是rc滤波器的主要优点，它得到广泛的应用并容易实现。通常用它来滤除所需频段以外的噪声。由于运算放大器的频率限制，有源滤波器通常用在约10khz以下的音频范围。对于像741那种有内部补偿的运算放大器，只限于在具有通带大约1khz以下的滤波器中使用。 图2.2.1所示为一阶低通滤波器，因为它只有一个单极点。贯穿本节内容，均假定运算放大器是理想的。定义基本反馈放大器的增益k和与它相关联的rc网络的0如下：极点为-0，零点为无限大。增益在低频为k，在0处下降3db，在很高频率时趋于零。通带从零延伸到0。rc滤波器与下一级或负载之间的缓冲由运算放大器来提供，运算放大器还产生电压增益。在某些应用中，图2.2.2的运算放大器被省掉了。图2.2.1的二阶低温滤波器有较尖锐的截止特性。求得其增益为其中0和k由式2.2.1定义。需要选择k来获得适当的极点。不难证明;如果k按式(2315)选择，那末式(2314)的二个极点是模为0，相角为的共轭复数。在2.2.2节中曾求出，无峰起最尖锐的截止特性发生在极点相角为45o的时候。，要选择45o的极点相角，放大器的增益应调节到3从式(2314)可以确定3db频率为0。三阶滤波器的滤波性能更有改进。它们有相同的0，但k值各异，总的增益便为式和式的乘积，即在节曾求出，三极点放大器获得无峰起最平坦响应的条件是三个极点的模相等，并且其中包含一对相角为60o的共轭复数。对上述选择，可以确定，式中的k22。3 直流电源供电子装备使用的电源在整个装备的成本、尺寸、重量、以及设计匠心上占有很大比重的情况是屡见不鲜的。当输入为交流电压时，直流电源一般有三个基本部件。这三个部件示于图3.1方框图中。整流器将输入交流变为带直流和交流两种分量的脉动波形。在某些应用场合，像电镀和电池充电，这种输出可以适用。但大多数应用都要求滤掉交流分量。滤波电路的输出对音频放大器和许多无线电接收机可能是合适的电源。但是，要使数字和模拟这两种集成电路正常工作，电源电压稳定常常是很重要的。本节扼要论述整流和滤波过程。电压稳定则是本窜其余部分的主题。 整流因图3.2所示为半波整流器电路，由二极管与负载电阻串联组成。市电频率输入电压通过二极管送出单向电流，后者在负载两端产生脉动电压。负载电压有非零的平均值vd c。 因此，整流器将输入交流电压转换成直流脉动电压。输出中有市电频率的各次谐波。当输人为60 hz时，图242输出波形中的频牢为0，60，120，180 hz，如此等等。用来规定电源输出中交流分量的指标为纹波因数r，定义为其中vac表示vl的交流分量的均方根值(不包括vdc)。不难推导，图242波形的总均方根值为0.5vm。，直流分量为。从式(241)求出纹波因数为1.21。对大多数用途，这个数值太大了。图3.3为全被桥式整流器。当vi为正，二极管d1和d2导通。另外两只二极管下半周导通。输出电压均方根值为，直流分量为2vm，所产生的纹波因数为0.48。当两只二极管相同时，输出中只出现市电频率的偶次谐波。对于60hz的输入，要滤掉的最低频率为120hz，此值为半波电路最低频率的两倍。滤波较容易。市电电压常因过高，必须降低。这时可在输入端加一只铁芯变压器。具有中心抽头变压器的全波整流器可用两只二极管组成，如图3.4所示。但是，每只二极管必须能承受的反巅电压应为整个次级线圈电压的最大瞬时值。6 外文原文及译文6.1 外文原文from charles aholt .electronic circuits digital and analog.1.1 basic amplifierstudies the amplifier, we first analyze the circuit of the chart 121, it contains a bias in the enlargement area npn transistor. although base sector width w is the collector voltage function, but in order to cause the discussion to simplify as far as possible, will neglect this secondary effect. therefore, ies and af regard as the constant. markin here as well as in entire this book, uses the standard symbolic representation electric current and the voltage. the electric current is ib is ib=ib+ib (12-1)when vi for zero, chart 121 electric circuit is called the static state, namely is at the dormant state, the static base current is ib；when vi is not the zero, difference of joint current ib and the quiescent value is ib. mark ib expresses the increase electric current, also is called ib signal component. attention: ib ，ib ，ib the custom reference direction take flows in the component the b end as. vbe expression from base extremely b to emitter electrode e loss of voltage, similarly wrote it quiescent voltage vbe and sum of the increase voltage vbe. chart in 121 electric circuit vbe is vi. in brief, the lowercase letter raises writes the subscript to express various joint currents and the total voltage; the capital letter raises writes the subscript to express various static quantity; the lowercase letter belt small letter subscript uses in various increases variable. stated not specially that, the electric current reference direction take flows in the component as. the voltage reference direction uses the double subscript, when or attempts in likely 12l vo such with the positive and negative symbolic representation, then q voltage and the electric current refer to the static quantity.chart 1.1 the amplifier14th chapter operational amplifierexcept that preceding flees has discussed altogether shoots, altogether the collection and altogether outside the base electric circuit, but also has another kind of specially important basic configuration, this is the differential amplifier. it has two signal voltage to input swiss and an in proportion to input signal interpolation output. frequently, from provides the negative feedback in the bleeder network to withdraw the output a part of achievement input voltage; but sometimes, an input end sweet and crisp earth. in these two kinds of situations, the differential amplifier all turns only then an input and an output single end amplifier.we will see to, the differential amplifier might process the big signal but not to have the oversized nonlinear distortion, moreover this big dynamic range will be one of its multitudinous characteristics. because bias not big time input impedance for center to high impedance, therefore the supply oscillator load cannot be overweight. in the low frequency work (including direct current) is possible. its electric circuit structure suits the sub-integrated circuit manufacture specially, thus the most linear integrated circuit contains level or the multistage differential amplifier. this kind of electric circuit example includes: the analog computer network, the monolithic voltage - stabilizer, the video amplifier, simulate the comparator and the operational amplifier. and following several deaf center enlarges in this chapter the operation 2e multi-purpose and the versatility does the key point is correct.the operational amplifier is has the difference input level the multistage structure, its characteristic for the voltage gain big, the input impedance high and the output impedance is low. it widely uses in many different types linearity and in the nonlinear circuit. using involves to the measuring appliance electric circuit, the special use linear amplifier, the oscillator, has the clothing filter and other electric circuits. in fact, every request is inexpensive voltage amplification situation, all should consider uses the operational amplifier. this chapter studies the operational amplifier some basic characteristics, certain applications also including. other questions then proposed in the following several chapters. shows in 15 chapter and in 17 chapter and succinctly discusses three kind of different operational amplifiers the electric circuit, let us from the differential amplifier start study.2 differential amplifieremitter coupling amplifierhas each kind of type the differential amplifier. the common electric circuit structure is arranges two bjt emitter electrode the increase series. solid illustration in chart 141 a. the ideal current supply provides constant direct current idc in this electric circuit. therefore, to emitter current increase ingredient ideal current supply for leads the way. its increase electric circuit has chart 141b the form. in the chart, the ideal direct current potential source and the current supply have used to short-circuit and to lead the way separately the substitution. obviously ie1-ie2 . the amplifier speaking of the increase electric current two emitter electrodes to connect (like chart 141 b two emitter electrodes such), is called the emitter coupling amplifier.more importantly transistor q1 and q2 must pair as far as possible, causes their characteristic nearly in to be consistent. when the transistor pair with the input voltage is a zero hour, two transistors collecting electrode electric currents are same. comes from the electric circuit symmetry to see this is obvious. even if abbreviates the q1 collection electricity level resistance, two electric currents almost are also equal, because works in the enlargement area bjt collecting electrode electric current has nothing to do with nearly with vce. thereupon, this resistance is sometimes abbreviated. retains its goal to lie in improvement direct current to be balanced. in the increase model, (its function the resistance which just like current supply) connects does not have what influence with the high impedance collecting electrode.input end a and b are q1 and the q2 base extreme. the increase model regarding the small signal is linear, may apply the principle of superposition. therefore, inputs us to two to be possible to process separately. make vs2 = 0, to this kind of situation, the increase electric circuit may draw becomes the two-pole amplifier the form,chart 2.1.2 emitter coupling amplifierchart 2.1.3 increase modellike chart 142 show. just like front had pointed out, the first level of rc influence may neglect. obviously this level is approximate is altogether the collection configuration, but second level then is altogether the base. this cascade input impedance is has same rs and the rx value altogether shoots the amplifier input impedance two times.so long as the load resistance is smaller than ro, in altogether collection and altogether in base two kinds of amplifier when to transmission may suddenly bribery resistance r and ro. makes the load by altogether the ground level low input impedance altogether the collection level obviously to satisfy this request. because load resistance rc is usually actual electric circuit in ro to be much smaller than, therefore the common base also satisfies this request. when vs1 = 0, joins vs2, the situation is similar. the output voltage then may from no matter what a collecting electrode obtains. in fact, we will see to, in two collecting electrodes resistances increase voltage scope equal but the mark will be opposite. therefore, the following will analyze neglects with the base sector width modulation related parameter.when supply oscillator resistance rs adds to the electric circuit, among frequency band increase model like chart 143 show. supposes two transistors is pairs, and has the same quiescent point and the increase parameter. each collecting electrode resistance rc and the collecting electrode increase current supply connects. therefore, these resistances do not affect the electric circuit the electric current. further said, if removes a resistance, does not change in addition in the resistance voltage. indicates ili2 in the emitter electrode pitch point node equation. obviously, two output voltages scope equal but the mark is opposite.bad mold voltage gain and altogether mold voltage gainexternal circuits return route equations obtain by chart 2.1.2output voltage voorci2，bad mold voltage gain ad defines difference of as the output voltage and two input voltages ratio, namelychart 2.1.4 among frequency band modeloutputs vo is the vo negative value. according to 165 center discussion, this kind of amplifier may serve as the phase-splitter. each output all in proportion to two inputs miss vs1vs2. this interpolation is called difference mold input voltage vd, namelytwo input voltages mean value is 1/2, represents altogether mold input voltage vc, thereforewhen two input voltages are altogether the mold increase by this equal output voltage ratio of with altogether the mold input voltage acregarding chart 143 electric circuits, when two input voltages equal output voltage is the zero, thus altogether the mold gain is the zero.so long as application chart 2.2.3 simplifications models, even if two transistors do not pair, altogether the mold increases also is a zero. to this kind of situation, may prove the electric current by the node equation: i1 and i2 each other has the direct ratio, thus works as two input voltages equal time two electric currents are the zero inevitably. however, if includes base sector width modulation resistance ro and r, is easy to prove to transistor which has not paired, usual ac is not a zero. therefore, although these resistances increase to the difference mold the influence may neglect, when calculates ac, in the model must include ro and r. chart 143 models including have not provided the static state emitter current the actual power source increase resistance. this resistance very is usually big, increases when the determination difference mold may neglect it. but in determined when ac, it is possibly important. even regarding the transistor which pairs, this resistance appears when the model, all can cause ac is not the zero. when low frequency, the ac value may be possible negative.difference of because of the request output in proportion to two inputs, therefore works as two inputs equal time outputs must be minimum. when ideal ac should be a zero. an important quality factor is altogether the mold rejection ratio (cmrr), it defines as or uses the full symmetry the electric circuit, uses the transistor which pairs and has the very high increase resistance the direct current source, may obtain the big cmrr value. usually, cmrr obtains by the experiment, its value possibly is bigger than 105 or 100 db. by already not cmrr and the ad value, may extract altogether the mold to increase ac the size, but cannot determine positively and negatively its.2.active rc filterthe filter permit or continue a transmission band, at the same time blocks outside these frequency bands the signal. in the low pass filter, the transmission band extends from the zero to some upper frequency. high passes the filter only through to be higher than some rating the frequency. also has the band pass filter and the band-elimination filter. falls the wave filter to filter out a very narrow frequency band, sometimes places it the amplifier in the feedback network by to obtain the narrow band pass filter. the passive filter by the resistance, the electric capacity, the inductance is composed, but the active rc filter by the resistance, the electric capacity and the active device are composed. removes the inductance is the rc filter main merit, it obtains the widespread application and is easy to realize. passes is commonly used it to filter needs outside the frequency band the noise. as a result of the operational amplifier frequency restriction, the active filter pass commonly used below approximately the 10khz audio frequency scope. regarding likes 741 that kinds the operational amplifier which has the interior to compensate, is only restricted in has below pass band probably 1khz in the filter to use.chart 2320 show for the first order low pass filter, because of it only then a simple pole. passes through this content, supposes the operational amplifier is ideal. defines the basic feedback amplifier gain k and with its correlation rc network 0 as follows:is not difficult from chart 2320 to extract the voltage gain forchart 2320 the first order low pass filterchart 2321 two steps low pass filterthe extreme is -0, the zero spot is an infinitely great. the gain in low frequency is k, in 0 drops 3db, when very high-frequency tends to the zero. the pass band extends from the zero to0. the rc filter provide with next level or the load between cushion by the operational amplifier, the operational amplifier also has the voltage gain. in certain applications, chart 2320 operational amplifiers are saved.chart 2321 two steps low temperatures filter have the incisive cut-off characteristic. obtains its gain is0 and k (2312) defines by the type. needs to choose k to obtain the suitable extreme. is not d