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1英文原文HOWLIGHTEMITTINGDIODESWORKLIGHTEMITTINGDIODES,COMMONLYCALLEDLEDS,AREREALUNSUNGHEROESINTHEELECTRONICSWORLDTHEYDODOZENSOFDIFFERENTJOBSANDAREFOUNDINALLKINDSOFDEVICESAMONGOTHERTHINGS,THEYFORMTHENUMBERSONDIGITALCLOCKS,TRANSMITINFORMATIONFROMREMOTECONTROLS,LIGHTUPWATCHESANDTELLYOUWHENYOURAPPLIANCESARETURNEDONCOLLECTEDTOGETHER,THEYCANFORMIMAGESONAJUMBOTELEVISIONSCREENORILLUMINATEATRAFFICLIGHTBASICALLY,LEDSAREJUSTTINYLIGHTBULBSTHATFITEASILYINTOANELECTRICALCIRCUITBUTUNLIKEORDINARYINCANDESCENTBULBS,THEYDONTHAVEAFILAMENTTHATWILLBURNOUT,ANDTHEYDONTGETESPECIALLYHOTTHEYAREILLUMINATEDSOLELYBYTHEMOVEMENTOFELECTRONSINASEMICONDUCTORMATERIAL,ANDTHEYLASTJUSTASLONGASASTANDARDTRANSISTORINTHISARTICLE,WELLEXAMINETHESIMPLEPRINCIPLESBEHINDTHESEUBIQUITOUSBLINKERS,ILLUMINATINGSOMECOOLPRINCIPLESOFELECTRICITYANDLIGHTINTHEPROCESSWHATISADIODEADIODEISTHESIMPLESTSORTOFSEMICONDUCTORDEVICEBROADLYSPEAKING,ASEMICONDUCTORISAMATERIALWITHAVARYINGABILITYTOCONDUCTELECTRICALCURRENTMOSTSEMICONDUCTORSAREMADEOFAPOORCONDUCTORTHATHASHADIMPURITIESATOMSOFANOTHERMATERIALADDEDTOITTHEPROCESSOFADDINGIMPURITIESISCALLEDDOPINGINTHECASEOFLEDS,THECONDUCTORMATERIALISTYPICALLYALUMINUMGALLIUMARSENIDEINPUREALUMINUMGALLIUMARSENIDE,ALLOFTHEATOMSBONDPERFECTLYTOTHEIRNEIGHBORS,LEAVINGNOFREEELECTRONSNEGATIVELYCHARGEDPARTICLESTOCONDUCTELECTRICCURRENTINDOPEDMATERIAL,ADDITIONALATOMSCHANGETHEBALANCE,EITHERADDINGFREEELECTRONSORCREATINGHOLESWHEREELECTRONSCANGOEITHEROFTHESEADDITIONSMAKETHEMATERIALMORECONDUCTIVEASEMICONDUCTORWITHEXTRAELECTRONSISCALLEDNTYPEMATERIAL,SINCEITHASEXTRANEGATIVELYCHARGEDPARTICLESINNTYPEMATERIAL,FREEELECTRONSMOVEFROMANEGATIVELYCHARGEDAREATOAPOSITIVELYCHARGEDAREAASEMICONDUCTORWITHEXTRAHOLESISCALLEDPTYPEMATERIAL,SINCEITEFFECTIVELYHASEXTRAPOSITIVELYCHARGEDPARTICLESELECTRONSCANJUMPFROMHOLETOHOLE,MOVINGFROMANEGATIVELYCHARGEDAREATOAPOSITIVELYCHARGEDAREAASARESULT,THEHOLESTHEMSELVESAPPEARTOMOVEFROMAPOSITIVELYCHARGEDAREATOANEGATIVELYCHARGEDAREAADIODECOMPRISESASECTIONOFNTYPEMATERIALBONDEDTOASECTIONOFPTYPEMATERIAL,WITHELECTRODESONEACHENDTHISARRANGEMENTCONDUCTSELECTRICITYINONLYONEDIRECTIONWHENNOVOLTAGEISAPPLIEDTOTHEDIODE,ELECTRONSFROMTHENTYPEMATERIALFILLHOLESFROMTHEPTYPEMATERIALALONGTHEJUNCTION2BETWEENTHELAYERS,FORMINGADEPLETIONZONEINADEPLETIONZONE,THESEMICONDUCTORMATERIALISRETURNEDTOITSORIGINALINSULATINGSTATEALLOFTHEHOLESAREFILLED,SOTHEREARENOFREEELECTRONSOREMPTYSPACESFORELECTRONS,ANDCHARGECANTFLOWTOGETRIDOFTHEDEPLETIONZONE,YOUHAVETOGETELECTRONSMOVINGFROMTHENTYPEAREATOTHEPTYPEAREAANDHOLESMOVINGINTHEREVERSEDIRECTIONTODOTHIS,YOUCONNECTTHENTYPESIDEOFTHEDIODETOTHENEGATIVEENDOFACIRCUITANDTHEPTYPESIDETOTHEPOSITIVEENDTHEFREEELECTRONSINTHENTYPEMATERIALAREREPELLEDBYTHENEGATIVEELECTRODEANDDRAWNTOTHEPOSITIVEELECTRODETHEHOLESINTHEPTYPEMATERIALMOVETHEOTHERWAYWHENTHEVOLTAGEDIFFERENCEBETWEENTHEELECTRODESISHIGHENOUGH,THEELECTRONSINTHEDEPLETIONZONEAREBOOSTEDOUTOFTHEIRHOLESANDBEGINMOVINGFREELYAGAINASARESULT,THEDEPLETIONZONEDISAPPEARSWHENTHENEGATIVEENDOFTHECIRCUITISHOOKEDUPTOTHENTYPELAYERANDTHEPOSITIVEENDISHOOKEDUPTOPTYPELAYER,ELECTRONSANDHOLESSTARTMOVINGIFTHEPTYPESIDEISCONNECTEDTOTHENEGATIVEENDOFTHECIRCUITANDTHENTYPESIDEISCONNECTEDTOTHEPOSITIVEEND,CURRENTWILLNOTFLOWNOCURRENTFLOWSACROSSTHEJUNCTIONBECAUSETHEHOLESANDTHEELECTRONSAREEACHMOVINGINTHEWRONGDIRECTIONWHENTHEPOSITIVEENDOFTHECIRCUITISHOOKEDUPTOTHENTYPELAYERANDTHENEGATIVEENDISHOOKEDUPTOTHEPTYPELAYER,THEDEPLETIONZONEGETSBIGGERTHEINTERACTIONBETWEENELECTRONSANDHOLESHASANINTERESTINGEFFECTITGENERATESLIGHTINTHENEXTSECTION,WELLFINDOUTEXACTLYWHYTHISISHOWCANADIODEPRODUCELIGHTLIGHTISAFORMOFENERGYTHATCANBERELEASEDBYANATOMITISMADEUPOFMANYSMALLPARTICLELIKEPACKETSTHATHAVEENERGYTHESEPARTICLES,CALLEDPHOTONS,ARETHEMOSTBASICUNITSOFLIGHTPHOTONSARERELEASEDASARESULTOFMOVINGELECTRONSINANATOM,ELECTRONSMOVEINORBITALSAROUNDTHENUCLEUSELECTRONSINDIFFERENTORBITALSHAVEDIFFERENTAMOUNTSOFENERGYGENERALLYSPEAKING,ELECTRONSWITHGREATERENERGYMOVEINORBITALSFARTHERAWAYFROMTHENUCLEUSFORANELECTRONTOJUMPFROMALOWERORBITALTOAHIGHERORBITAL,SOMETHINGHASTOBOOSTITSENERGYLEVELCONVERSELY,ANELECTRONRELEASESENERGYWHENITDROPSFROMAHIGHERORBITALTOALOWERONETHISENERGYISRELEASEDINTHEFORMOFAPHOTONAGREATERENERGYDROPRELEASESAHIGHERENERGYPHOTON,WHICHISCHARACTERIZEDBYAHIGHERFREQUENCYASWESAWINTHELASTSECTION,FREEELECTRONSMOVINGACROSSADIODECANFALLINTOEMPTYHOLESFROMTHEPTYPELAYERTHISINVOLVESADROPFROMTHECONDUCTIONBANDTOALOWERORBITAL,SOTHEELECTRONSRELEASEENERGYINTHEFORMOFPHOTONSTHISHAPPENSINANYDIODE,BUTYOUCANONLYSEETHEPHOTONSWHENTHEDIODEISCOMPOSEDOFCERTAINMATERIALTHEATOMSINASTANDARDSILICONDIODE,FOREXAMPLE,ARE3ARRANGEDINSUCHAWAYTHATTHEELECTRONDROPSARELATIVELYSHORTDISTANCEASARESULT,THEPHOTONSFREQUENCYISSOLOWTHATITISINVISIBLETOTHEHUMANEYEITISINTHEINFRAREDPORTIONOFTHELIGHTSPECTRUMTHISISNTNECESSARILYABADTHING,OFCOURSEINFRAREDLEDSAREIDEALFORREMOTECONTROLS,AMONGOTHERTHINGSVISIBLELIGHTEMITTINGDIODESVLEDS,SUCHASTHEONESTHATLIGHTUPNUMBERSINADIGITALCLOCK,AREMADEOFMATERIALSCHARACTERIZEDBYAWIDERGAPBETWEENTHECONDUCTIONBANDANDTHELOWERORBITALSTHESIZEOFTHEGAPDETERMINESTHEFREQUENCYOFTHEPHOTONINOTHERWORDS,ITDETERMINESTHECOLOROFTHELIGHTWHILEALLDIODESRELEASELIGHT,MOSTDONTDOITVERYEFFECTIVELYINANORDINARYDIODE,THESEMICONDUCTORMATERIALITSELFENDSUPALOTOFTHELIGHTENERGYLEDSARESPECIALLYCONSTRUCTEDTORELEASEALARGENUMBEROFPHOTONSOUTWARDADDITIONALLY,THEYAREHOUSEDINAPLASTICBULBTHATCONCENTRATESTHELIGHTINAPARTICULARDIRECTIONLEDSHAVESEVERALADVANTAGESOVERCONVENTIONALINCANDESCENTLAMPSFORONETHING,THEYDONTHAVEAFILAMENTTHATWILLBURNOUT,SOTHEYLASTMUCHLONGERADDITIONALLY,THEIRSMALLPLASTICBULBMAKESTHEMALOTMOREDURABLETHEYALSOFITMOREEASILYINTOMODERNELECTRONICCIRCUITSBUTTHEMAINADVANTAGEISEFFICIENCYINCONVENTIONALINCANDESCENTBULBS,THELIGHTPRODUCTIONPROCESSINVOLVESGENERATINGALOTOFHEATTHISISCOMPLETELYWASTEDENERGY,UNLESSYOUREUSINGTHELAMPASAHEATERLEDSGENERATEVERYLITTLEHEAT,RELATIVELYSPEAKINGAMUCHHIGHERPERCENTAGEOFTHEELECTRICALPOWERISGOINGDIRECTLYTOGENERATINGLIGHT,WHICHCUTSDOWNONTHEELECTRICITYDEMANDSCONSIDERABLYUPUNTILRECENTLY,LEDSWERETOOEXPENSIVETOUSEFORMOSTLIGHTINGAPPLICATIONSTHEPRICEOFSEMICONDUCTORDEVICESHASPLUMMETEDOVERTHEPASTDECADE,HOWEVER,MAKINGLEDSAMORECOSTEFFECTIVELIGHTINGOPTIONFORAWIDERANGEOFSITUATIONSWHILETHEYMAYBEMOREEXPENSIVETHANINCANDESCENTLIGHTSUPFRONT,THEIRLOWERCOSTINTHELONGRUNCANMAKETHEMABETTERBUYINTHEFUTURE,THEYWILLPLAYANEVENBIGGERROLEINTHEWORLDOFTECHNOLOGYTRANSIENTVOLTAGESUPPRESSORTVSDIODEPRESENTATIONHIGHPROTECTIONONSENSITIVEMOBILEELECTRONICDEVICESFOLLOWSTRICTLYTOTHEIEC6100042ESDTESTSTANDARDUSINGTHEBEHAVIOROFDIODEP/NJUNCTIONTOACHIEVEESDPROTECTIONWHATARETRANSIENTVOLTAGESTHESEAREFAULTSWHICHCAUSETHEVOLTAGETOGOOUTSIDENORMALLIMITSFORAPERIODOFTIMETRANSIENTVOLTAGESARECHARACTERIZEDBYTHREETHINGSVERYHIGHVOLTAGE,OCCURFORAVERYSHORTPERIODOFTIMEINNANOSECONDSANDHIGHOCCURRENCEMANYTRANSIENTSCAUSEDAMAGETOMICROSEMICONDUCTORCHIPSETSBYDEGRADINGTHEIRPERFORMANCETHISDAMAGEISCUMULATIVEANDEVENTUALLYREACHESAPOINTWHERESUDDENANDCOMPLETEFAILUREOF4THECOMPONENTRESULTSMOREOVER,SOMETRANSIENTSARECAPABLEOFCAUSINGIMMEDIATEEQUIPMENTFAILURESEQUIPMENTFAILURESCAUSEDBYTRANSIENTSAREHARDTODETECTANDAREOFTENINCORRECTLYBLAMEDONOTHER‘PERCEIVED’CAUSESMICROSEMICONDUCTORCHIPSETSDAMAGEDBYTRANSIENTSOFTENREQUIRESOPHISTICATEDINSTRUMENTTOREPLACETHEMWHICHMAKETHEMEXPENSIVETOREPAIRTHEONLYCUREISTOCLAMPTRANSIENTSTOASAFELEVELWHERETHEPROTECTEDLOADCANWITHSTANDTVSDIODE’SADVANTAGESTVSDIODEVSZENERDIODECOMPAREDWITHTHETRADITIONALZENERDIODE,TVSDIODEHASALARGERP/NCROSSSECTIONTVSDIODECOMPONENTISCONSTRUCTEDANDDESIGNEDTOABSORBLARGERAMOUNTSOFENERGY,JOULES,WITHAFASTERRESPONSETIMETHANZENERDIODEZENERDIODEHASAHIGHERCLAMPINGVOLTAGEANDHEATDISSIPATIONISSLOWERTVSDIODEVSMULTILAYERMETALOXIDEVARISTOR,MLVAMAJORDIFFERENCEBETWEENTVSDIODEANDMLVIS,ASMLVABSORBSTRANSIENTENERGY,ITSELECTRICALPARAMETERSSUCHASLEAKAGECURRENTANDBREAKDOWNVOLTAGETENDTODRIFTAWAYFROMTHEIRORIGINALSPECIFICATIONSWHICHEXHIBITSANINHERENTWEAROUTMECHANISMWITHINTHESTRUCTUREBECAUSEOFITSHIGHIMPEDANCE,ITSCLAMPINGRATIOCANREACHASHIGHAS3THEREFOREMLVISMORESUITABLETOBEAPPLIEDONLESSSENSITIVELINESWHEREITSHIGHCLAMPINGVOLTAGECANBETOLERATEDTVSDIODEVSCERAMICCAPACITORCERAMICCAPACITORISNOTABLETOWITHSTANDAHIGHTRANSIENTVOLTAGEA10KVTRANSIENTVOLTAGEWILLDESTROYABOUT60OFTHECOMPONENTOFTHECERAMICCAPACITORWHILETVSDIODEISABLETOWITHSTANDUPTO15KVTRANSIENTVOLTAGECERAMICCAPACITORISALSONOTABLETODISSIPATEHEATEFFICIENTLYLIKEWHATTVSDIODEDOESWHENTRANSIENTOCCURSTVSDIODEVSGASDISCHARGETUBES,GDTSTVSDIODELIMITSVOLTAGESPIKETOACCEPTABLELEVELBYCLAMPINGWHILEGDTLIMITSVOLTAGESPIKEBYCROWBARACTIONGDTCONDUCTSWHENITSTHRESHOLDVOLTAGEISEXCEEDEDANDTHENTRIGGERTOANONSTATEVOLTAGEOFONLYAFEWVOLTSADRAWBACKOFGDTPROTECTIONISTHATTHETRIGGERONSTATEVOLTAGEISBELOWTHEOPERATINGVOLTAGEOFTHEPROTECTEDLOADTHEPROTECTEDLOADWILLBESHUTDOWNTEMPORARILY
