Unit6OperationalAmplifierTextKeywordsTechnicaltermsExpressionsNotestothetextText

Theoperationalamplifierisoneofthemostwidelyusedanalogintegratedcircuits.Actually,itisthemultileveldirectcouplingamplifierwithhighgain,highinputimpedanceandlowoutputimpedance.Withthedevelopmentofintegratedcircuittechnology,theperformancehasbeenmoreperfect.Today,thedevelopmentdirectionofintegratedoperationalamplifierislowerdrift,noiseandpowerdissipation;higherspeed,gainandinputvoltage;moreovermuchmoreoutputpoweretc.

Therearemanystylesofoperationalamplifiers.Thecircuitsarenotsosame,butgenerallythecircuitsconsistofthreestages(asshowninFig.6-1):input,middleandoutputstage.Normally,theinputcircuitisthedifferentialamplifierusedtoreducethezerodrift.Theprimarypurposeofthemiddlestageistoobtainhighvoltagegain.Theoutputstageismadeupofthevoltagefollowertodecreasetheoutputimpedanceandimprovetheoutputpowerandtheloadcapability.Fig.6-1theconstituteframeofintegratedcircuit

Theoperationalamplifieristhemostimportantbasicbuildingblockofalllinearcircuits.Ithasawiderangeofapplicationsinsuchfieldsasanaloguesignaloperations,amplification,filtering,waveformsproducing,linearandnon-linearsignalshandling,etc.

Theterm“operationalamplifier”wasoriginallyappliedtohighgainamplifiersoperatingdowntozerofrequencywhichwereusedinanaloguecomputerstoperformcertainmathematicaloperations.Thesehighgainamplifiersarenowusedforawidevarietyofapplications,butthename“operationalamplifiers”or“op-amp”isnormallyusedeventhoughnomathematicaloperationareinvolved.Theearlyoperationalamplifiersemployeddiscretecomponents,butitisnowmuchmoreconvenienttoemployanintegratedcircuit.Thecircuitdesignersarenotgenerallyinterestedintheinternalcomponentsofanintegratedcircuit,butonlyintheperformanceoftheunitasawhole.Therefore,thesymbolinFig.6-2isusedtodenotetheamplifier.Itcanbeseenthattherearetwoinputsoneoutputandconnectionstothepositiveandnegativesupplylines.Fig.6-2theICsymbol

Iftheinvertinginputismadeslightlymorepositive,theoutputwillbecomemorenegative,thisiswhythename“inverting”?isgiventothisinput.If,however,thenon-invertinginputismademorepositive,theoutputwillalsobecomemorepositive.

Type741deviceisoneofthebestknowngeneralpurposeoperationalamplifiersandisalsooneofthecheapestofalllinearintegratedcircuits.Thedeviceisactuallyavailableinanumberofdifferentpackages.Readerswillusuallyfindthetypeof741showninFig.6-3.Thistypeofpackageisknownasthe8pindual-in-line.Fig.6-3thetypeof741

Abasiccircuitofa741invertingamplifierisshowninFig.6-4.Theinputsignalisfedtotheinvertinginputofthe741viaR1andthereforetheoutputisinvertedinphasewithrespecttotheinput.Operationalamplifiersaredesignedtohaveveryhighinputimpedance.Theinputcurrentsofthe741circuitarethereforeverysmall.Astheinvertinginputisvirtuallyatgroundpotential,thecurrentwhichflowsthroughR1isequaltotheinputvoltageuidividedbyR1.Similarly,thecurrentflowingthroughR3is

uo/R3whereuoistheoutputvoltage.Thesetwocurrentsarealmostequal,thusthevoltagegainofcircuitisequaltotheresistorvaluesG?=?－R3/R1.Fig.6-4741invertingamplifierKeywords

multilevel n.多級

couple vt.連合，連接，結(jié)合

drift n.漂移

differential adj.差動的

capability

n.(實際)能力，性能

analog

n.模擬；adj.模擬的

amplification

n.擴大

filter

n.濾波器；vt.過濾

frequency

n.頻率

variety

n.變化，多樣性，種類

convenient

adj.便利的，方便的

internal

adj.內(nèi)在的，國內(nèi)的

denote

vt.指示，表示

invert

vt.使顛倒，使轉(zhuǎn)化

available

adj.可用到的，可利用的

package

n.包裹，包，管殼

pin

n.釘，管腳，引線

virtually

adv.事實上，實質(zhì)上Technicalterms

operationalamplifier 運算放大器

directcouplingamplifier 直接耦合放大器

powerdissipation 功耗

zerodrift 零點漂移

voltagefollower 電壓跟隨器

linearandnon-linearsignalshandling線性和非線性信號處理

invertinginput 反相輸入端

non-invertinginput 同相輸入端

8pindual-inline 8管腳雙列直插式Expressions

avarietyof 各種各樣的

eventhough 即使

beinterestedin... 對…感興趣

beknownas... 被稱為…

withrespectto 關(guān)于，至于Notestothetext

1.?Normally,theinputcircuitisthedifferentialamplifierusedtoreducethezerodrift.

一般來說，輸入級是差動放大器，用于減小零漂。句中的“usedtoreducethezerodrift”為過去分詞作后置定語，修飾前面的“amplifier”。

2.?Theoutputstageismadeupofthevoltagefollowertodecreasetheoutputimpedanceandimprovetheoutputpowerandtheloadcapability.

輸出級由電壓跟隨器構(gòu)成，用于減小輸出阻抗，提高輸出功率和帶負(fù)載能力。句中，“bemadeupof”意為由…構(gòu)成，為被動語態(tài)；動詞不定式“todecrease…andimprove…”作目的狀語，“improve”前面承前省略“to”。

3.?Theterm“operationalamplifier”wasoriginallyappliedtohighgainamplifiersoperatingdowntozerofrequencywhichwereusedinanaloguecomputers