电子专业英语教学课件作者高明辉第8章.ppt

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1、Warming-upI.Canyoupointoutthenameofthefollowingpictures?II.Doyouknowwhatthefollowingabbreviationsorsymbolsstandfor?KVLKCLP-NjunctionUnit8Diodes下一页返回III.TalkaboutCurrentinEnglish.Andthefollowingpatternsyoucanuse:Doyouknowadiode?Couldyoutellmehowmanykindsofdiodesthereare?Andwhataret

2、hey?Whatisadiodesusuallyusedas?TextComprehensionDiodeAsemiconductordiodeisatwo—terminaldevice,containingasingleP-Njunctionwithtwoleads,ananodeandacathode.Thediodeallowscurrenttoflowinonlyonedirection.ThegeneralcircuitsymbolforadiodeisshowninFig-1alongwithitsrelationshiptotheP—Nstr

3、ucture.Unit8Diodes上一页下一页返回Adiodeisforwardbiasedwhenthevoltageofitsanodeishigherthanthevoltageofitscathode.Insuchsituation,currentwillflow.Whenthediodeisreversebiased,i.e.thevoltageofitsanodeislowerthanthevoltageofitscathode,itcausesnocurrent.Generally,diodeapplicationscanbeclassif

4、iedaccordingtothethreeregionsofdiodeoperation.Switchingandrectifyingapplicationsinvolvetransitionsbetweenthereverse—biasandforward—biasregion.Insuchapplications,caremustbetakentochooseadiodewithareversebreakdownvoltagelargeenoughtopreventundesiredreversebreakdown.Adiodeisusuallyus

5、edasarectifierbecauseofitscharacteristic.Thevalueofarectifierisexpressedinamperes.Furthermoretherearenumeroustypesofdiodes,suchasZenerdiodes,photodiodes,light—emittingdiodesetc.Unit8Diodes上一页下一页返回Thediodeisthefirstnetworkelementweencounterthatisstrikinglynonlinearinthemiddleofitsn

6、ormaloperatingrange.BothKVLandKCLcanbeused,sincetheirvaliditydoesnotdependonthelinearityornonlinearityofthenetworkelements.However,wemustbecarefulintheuseofsuperposition,Theveninequivalents,andNortonequivalents,becausethesemethodsareexplicitlyrestrictedtolinearnetworks.Wecansepara

7、tethelinearnetworkfromthenonlinearelementsandcarryoutagraphicalsolutionforthevoltageandcurrentinthenonlinearelements.VocabularySemiconductorn.半导体reverseadj.相反的反向的junctionn.连接，交叉点classifyvt.把…分类leadn.导线rectifyvt.把…整流anoden.阳极，正极rectifiern.整流器Unit8Diodes上一页下一页返回cathoden.阴极characteri

8、sticn.特征，特性biasedadj.偏置的，偏压的amper