電子電路 數(shù)字模擬 外文翻譯 外文文獻(xiàn) 英文文獻(xiàn) 電子電路 數(shù)字與模擬 下冊

1、1外文譯文節(jié)選自 （美）c.a.霍爾特 電子電路 數(shù)字與模擬 下冊1 .1基本放大器研究放大器，我們首先分析圖1.1的電路，它包含一個偏置于放大區(qū)的npn晶體管。雖然基區(qū)寬度w是集電極電壓的函數(shù)，但為了使討論盡可能簡化，將忽略這個次要的效應(yīng)。因此，ies和af看作常數(shù)。符號在這里以及整個這本書中，采用標(biāo)準(zhǔn)符號表示電流和電壓。電流為ib 為ib=ib+ib 圖 1.1當(dāng)vi為零時，圖1.1 的電路叫做靜態(tài)，即處于休止?fàn)顟B(tài)，靜態(tài)基極電流為ib；當(dāng)vi不為零時，總電流ib與靜態(tài)值之差為ib。 符號ib表示增量電流，也稱為ib的信號分量。注意：ib ，ib ，ib的習(xí)慣參考方向均以流入器件的b端為正。

2、vbe表示從基極b到發(fā)射極e的電壓降，同樣把它寫成靜態(tài)電壓vbe和增量電壓vbe之和。圖121電路中vbe就是vi?？傊懽帜笌Т髮懴聵?biāo)表示各總電流和總電壓；大寫字母帶大寫下標(biāo)表示各靜態(tài)量；小寫字母帶小寫下標(biāo)用于各增量變量。不特別聲明，電流參考方向均以流入器件為正。電壓參考方向用雙下標(biāo)，或象圖2.1中vo那樣用正負(fù)符號表示時，則q點的電壓和電流均指靜態(tài)量。圖1.12 運(yùn)算放大器除前一章討論過的共射、共集和共基電路以外，還有另一種特別重要的基本組態(tài)，這就是差分放大器。它有兩個信號電壓輸入瑞和一個正比于輸入信號差值的輸出端。常常，從提供負(fù)反饋的分壓網(wǎng)絡(luò)上提取輸出的一部分作為一個輸入電壓；而有時

3、，一個輸入端甘脆接地。在這兩種情況下，差分放大器都變成只有一個輸入和一個輸出的單端放大器。我們將看到，差分放大器可以處理較大的信號而沒有過大的非線性失真，而且這個較大的動態(tài)范圍是它的眾多特性之一。由于偏流不大時輸入阻抗為中到高阻抗，所以信號源負(fù)載不會過重。在低頻工作(包括直流)是可能的。其電路結(jié)構(gòu)特別適合子集成電路制造，因而多數(shù)線性集成電路包含一級或多級差分放大器。這類電路的實例有：模擬計算機(jī)網(wǎng)絡(luò)、單片穩(wěn)壓器、視頻放大器、模擬比較器和運(yùn)算放大器。在本章和后續(xù)幾聾中把運(yùn)算放大2e的多功能性和通用性作重點是正確的。運(yùn)算放大器是具有差分輸入級的多級結(jié)構(gòu)，其特征為電壓增益大、輸入阻抗高和輸出阻抗低。它

4、廣泛用于許多不同類型的線性和非線性電路中。應(yīng)用涉及到儀表電路、特殊用途的線性放大器、振蕩器、有服濾波器及其他電路。事實上，凡是要求廉價電壓放大的場合，都應(yīng)考慮采用運(yùn)算放大器。本章研究運(yùn)算放大器的一些基本特性，若干應(yīng)用也包括在內(nèi)。其他問題則將在后續(xù)幾章中提出。在15章和17章中示出并扼要討論三種不同的運(yùn)算放大器的電路，讓我們從差分放大器開始學(xué)起。2.1 差分放大器射極耦合放大器有各種類型的差分放大器。常見的電路結(jié)構(gòu)是把兩個bjt的發(fā)射極安排成增量串聯(lián)。實例示于圖2.1.1。在該電路中理想電流源提供恒定的直流電流idc。因此，對發(fā)射極電流的增量成分理想電流源為開路。其增量電路具有圖141b的形式。

5、圖中，理想的直流電壓源及電流源已分別用短路和開路代換。顯然ie1-ie2。就增量電流而言放大器的兩個發(fā)射極相串聯(lián)(如圖2.1.2的兩個發(fā)射極那樣)，稱為射極耦合放大器。重要的是晶體管q1和q2要盡可能配對，使它們的特性近于一致。當(dāng)晶體管配對和輸入電壓為零時，兩個晶體管的集電極電流就相同。從電路對稱性來看這是明顯的。即使省略ql的集電級電阻，兩個電流也差不多相等，因為工作于放大區(qū)的bjt的集電極電流與vce幾乎無關(guān)。于是，該電阻有時被省略。保留它的目的在于改善直流平衡。在增量模型中，與高阻抗集電極(其作用宛如電流源)相串聯(lián)的電阻沒有什么影響。輸入端a和b是q1和q2的基極端。增量模型對于小信號是

6、線性的，可應(yīng)用迭加原理。因此，對兩個輸入我們可以分別處理。令vs20，對這種情況,增量電路可畫成兩極放大器的形式，圖2.1.1 完整電路圖2.1.2 增量模型圖2.1.3 增量模型 如圖2.1.2所示。正如前面指出過的，第一級rc的影響可以忽略?？梢娺@級近似為共集組態(tài)，而第二級則為共基。該級聯(lián)的輸入阻抗是具有相同rs和rx值的共射放大器輸入阻抗的兩倍。只要負(fù)載電阻小于ro，在共集和共基兩種放大器中在正向傳輸時可忽賂電阻r和ro。以共基級低輸入阻抗作負(fù)載的共集級顯然滿足這個要求。因為負(fù)載電阻rc通常比實際電路中的ro小得多，所以共基極也滿足這個要求。當(dāng)vs10，加入vs2時，情況是相似的。輸出電

7、壓則可從任一集電極取得。事實上，我們將看到，兩個集電極電阻上的增量電壓幅度相等而符號相反。因此，以下分析將忽略與基區(qū)寬度調(diào)制有關(guān)的參數(shù)。當(dāng)信號源電阻rs加到電路時，中間頻段的增量模型如圖 2.1.3所示。假定兩只晶體管是配對的，并有同樣的靜態(tài)點和增量參數(shù)。每個集電極電阻rc與集電極增量電流源相串聯(lián)。因此，這些電阻不影響電路的電流。進(jìn)一步說，如果去掉一個電阻，不改變另電阻上的電壓。在發(fā)射極節(jié)點的節(jié)點方程表明ili2。顯然，兩個輸出電壓幅度相等而符號相反。差模電壓增益與共模電壓增益由圖2.1.4外電路的回路方程求得 （2.1.1）輸出電壓voorci2，差模電壓增益ad定義為輸出電壓與兩個輸入電壓

8、之差的比，即 （2.1.2） 圖 2.1.4 模型之間的頻帶 輸出vo是vo的負(fù)值。據(jù)165節(jié)中的討論，這種放大器可用作分相器。每個輸出都正比于兩個輸入之差vs1vs2。該差值叫做差模輸入電壓vd，即兩個輸入電壓的平均值是1/2(vs1+vs2)，代表共模輸入電壓vc,因此當(dāng)兩個輸入電壓被此相等時輸出電壓與共模輸入電壓之比是共模增益ac對于圖 2.1.3的電路，當(dāng)兩個輸入電壓相等時輸出電壓為零，因而共模增益為零。只要應(yīng)用圖 2.1.3的簡化模型，即使兩只晶體管不配對，共模增益也為零。對這種情況，由節(jié)點方程可證明電流：i1和i2彼此成正比，因而當(dāng)兩個輸入電壓相等時兩個電流必然為零。然而，如果計入

9、基區(qū)寬度調(diào)制電阻ro和r，容易證明對未配對的晶體管，通常ac不為零。因此，盡管這些電阻對差模增益的影響可忽略，在計算ac時，模型中應(yīng)當(dāng)包括ro和r。圖2.1.3的模型并沒有包括提供靜態(tài)發(fā)射極電流的實際電源的增量電阻。這個電阻通常很大，在確定差模增益時可把它忽略。但在確定ac時，它可能是重要的。甚至對于配對的晶體管，這個電阻在模型中出現(xiàn)時，都會使ac不為零。在低頻時，ac值可正可負(fù)。因為要求輸出正比于兩個輸入之差，所以當(dāng)兩個輸入相等時輸出應(yīng)當(dāng)極小。理想時ac應(yīng)為零。一個重要的品質(zhì)因數(shù)是共模抑制比(cmrr)。 使用完全對稱的電路，采用配對的晶體管和具有很高增量電阻的直流電流源，可以獲得較大的cm

10、rr值。通常，cmrr由實驗求得，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，但不能確定其正負(fù)。2.2 有源rc濾波器濾波器允許一個或不止一個傳輸頻帶，同時阻斷這些頻帶以外的信號。在低通濾波器中，傳輸頻帶從零延伸到某個最高頻率。高通濾波器只通過高于某個規(guī)定值的頻率。還有帶通濾波器和帶阻濾波器。陷波濾波器濾掉一個很窄的頻帶，有時把它放在放大器的反饋網(wǎng)絡(luò)中以獲得窄帶帶通濾波器。無源濾波器由電阻、電容、電感組成，而有源rc濾波器由電阻、電容和有源器件組成。去掉電感是rc濾波器的主要優(yōu)點，它得到廣泛的應(yīng)用并容易實現(xiàn)。通常用它來濾除所需頻段以外的噪聲。由于運(yùn)算放

11、大器的頻率限制，有源濾波器通常用在約10khz以下的音頻范圍。對于像741那種有內(nèi)部補(bǔ)償?shù)倪\(yùn)算放大器，只限于在具有通帶大約1khz以下的濾波器中使用。 圖2.2.1所示為一階低通濾波器，因為它只有一個單極點。貫穿本節(jié)內(nèi)容，均假定運(yùn)算放大器是理想的。定義基本反饋放大器的增益k和與它相關(guān)聯(lián)的rc網(wǎng)絡(luò)的0如下：極點為-0，零點為無限大。增益在低頻為k，在0處下降3db，在很高頻率時趨于零。通帶從零延伸到0。rc濾波器與下一級或負(fù)載之間的緩沖由運(yùn)算放大器來提供，運(yùn)算放大器還產(chǎn)生電壓增益。在某些應(yīng)用中，圖2.2.2的運(yùn)算放大器被省掉了。圖2.2.1的二階低溫濾波器有較尖銳的截止特性。求得其增益為其中0和

12、k由式2.2.1定義。需要選擇k來獲得適當(dāng)?shù)臉O點。不難證明;如果k按式(2315)選擇，那末式(2314)的二個極點是模為0，相角為的共軛復(fù)數(shù)。在2.2.2節(jié)中曾求出，無峰起最尖銳的截止特性發(fā)生在極點相角為45o的時候。，要選擇45o的極點相角，放大器的增益應(yīng)調(diào)節(jié)到3從式(2314)可以確定3db頻率為0。三階濾波器的濾波性能更有改進(jìn)。它們有相同的0，但k值各異，總的增益便為式和式的乘積，即在節(jié)曾求出，三極點放大器獲得無峰起最平坦響應(yīng)的條件是三個極點的模相等，并且其中包含一對相角為60o的共軛復(fù)數(shù)。對上述選擇，可以確定，式中的k22。3 直流電源供電子裝備使用的電源在整個裝備的成本、尺寸、重量

13、、以及設(shè)計匠心上占有很大比重的情況是屢見不鮮的。當(dāng)輸入為交流電壓時，直流電源一般有三個基本部件。這三個部件示于圖3.1方框圖中。整流器將輸入交流變?yōu)閹е绷骱徒涣鲀煞N分量的脈動波形。在某些應(yīng)用場合，像電鍍和電池充電，這種輸出可以適用。但大多數(shù)應(yīng)用都要求濾掉交流分量。濾波電路的輸出對音頻放大器和許多無線電接收機(jī)可能是合適的電源。但是，要使數(shù)字和模擬這兩種集成電路正常工作，電源電壓穩(wěn)定常常是很重要的。本節(jié)扼要論述整流和濾波過程。電壓穩(wěn)定則是本竄其余部分的主題。 整流因圖3.2所示為半波整流器電路，由二極管與負(fù)載電阻串聯(lián)組成。市電頻率輸入電壓通過二極管送出單向電流，后者在負(fù)載兩端產(chǎn)生脈動電壓。負(fù)載電壓

14、有非零的平均值vd c。 因此，整流器將輸入交流電壓轉(zhuǎn)換成直流脈動電壓。輸出中有市電頻率的各次諧波。當(dāng)輸人為60 hz時，圖242輸出波形中的頻牢為0，60，120，180 hz，如此等等。用來規(guī)定電源輸出中交流分量的指標(biāo)為紋波因數(shù)r，定義為其中vac表示vl的交流分量的均方根值(不包括vdc)。不難推導(dǎo)，圖242波形的總均方根值為0.5vm。，直流分量為。從式(241)求出紋波因數(shù)為1.21。對大多數(shù)用途，這個數(shù)值太大了。圖3.3為全被橋式整流器。當(dāng)vi為正，二極管d1和d2導(dǎo)通。另外兩只二極管下半周導(dǎo)通。輸出電壓均方根值為，直流分量為2vm，所產(chǎn)生的紋波因數(shù)為0.48。當(dāng)兩只二極管相同時，

15、輸出中只出現(xiàn)市電頻率的偶次諧波。對于60hz的輸入，要濾掉的最低頻率為120hz，此值為半波電路最低頻率的兩倍。濾波較容易。市電電壓常因過高，必須降低。這時可在輸入端加一只鐵芯變壓器。具有中心抽頭變壓器的全波整流器可用兩只二極管組成，如圖3.4所示。但是，每只二極管必須能承受的反巔電壓應(yīng)為整個次級線圈電壓的最大瞬時值。6 外文原文及譯文6.1 外文原文from charles aholt .electronic circuits digital and analog.1.1 basic amplifierstudies the amplifier, we first analyze the c

16、ircuit 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. m

17、arkin 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；w

18、hen 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

19、 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 rai

20、ses 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 subscr

21、ipt, 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 th

22、e 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 n

23、egative 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 diff

24、erential 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

25、 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

26、 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 ope

27、rational 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 applian

28、ce 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 b

29、asic 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

30、 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

31、 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 se

32、parately 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

33、 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

34、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.

35、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

36、 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 fro

37、nt 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

38、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 obvious

39、ly 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 ob

40、tains. 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 circui

41、t, 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 affec

42、t 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

43、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. accordi

44、ng 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, theref

45、orewhen 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

46、 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

47、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, i

48、n 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 possibl

49、y 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 tim

50、e 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

51、 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

52、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 filt

53、er 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 a

54、ctive 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

55、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

56、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

57、 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

58、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