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Logic gates are a vital part of many digital circuits, and as such, every kind is available as an IC. For examples, see the 4000 series of CMOS logic chips ... Wikitronics Explore MainPage AllPages Community InteractiveMaps RecentBlogPosts WikiContent RecentlyChangedPages Doublediode Rectifierdiode InteractingwithPhoenix-M Logicgate Digitalelectronics CMOS Inductor Logicgates ANDgate ORgate NOTgate XORgate XNORgate NANDgate NORgate Semiconductors Diode Transistor Zenerdiode Photosensitivediode Rectifierdiode Tunneldiode Community Help FANDOM Games Anime Movies TV Video Wikis ExploreWikis CommunityCentral StartaWiki Register Don'thaveanaccount? SignIn Advertisement Logicgate Edit Editsource History Talk(0) watch 01:54 Obi-WanFinale-TheLoop Doyoulikethisvideo? PlaySound Andlogicgateperformsalogicaloperationononeormorelogicinputsandproducesasinglelogicoutput.ThelogicnormallyperformedisBooleanlogicandismostcommonlyfoundindigitalcircuits.Logicgatesareprimarilyimplementedelectronicallyusingdiodesortransitors,butcanalsobeconstructedusingelectromagneticrelays,fluidics,optics,orevenmechanicalelements. Contents 1Logicgates 2Logicgatesandhardware 3Symbols 3.1ListofLogicGateICs 4DeMorganequivalentsymbols 5Storageofbits8inabyte 6Three-statelogicgates 7Miscellaneous 8Historyanddevelopment 9References 10Furtherreading Logicgates[] Alogicgatetakesoneormorelogic-levelinputsandproducesasinglelogic-leveloutput.Becausetheoutputisalsoalogiclevel,anoutputofonelogicgatecanconnecttotheinputofoneormoreotherlogicgates.Twooutputsareneverconnectedtogetherastheycouldproduceconflictinglogicvalues.Inelectroniclogicgates,thiswouldcauseashortcircuit. Inelectroniclogic,alogiclevelisrepresentedbyacertainvoltage(thisiswrong .Eachlogicgaterequirespowersothatitcansourceandsinkcurrentstoachievethecorrectoutputvoltage.Inlogiccircuitdiagramsthepowerisnotshown,butinafullelectronicschematic,powerconnectionsarerequired. Thesimplestformofelectroniclogicislogic.ThisallowsANDandORgatestobebuilt,butnotinverters,andsoisanincompleteformoflogic.Tobuildacompletelogicsystem,aorcanbeused.Thesimplestfamilyoflogicgatesusingbipolartransistorsiscalledmetadata-rte-instance,fromachangeininputofagatetothecorrespondingchangeinitsoutput.Whengatesarecascaded,thetotalpropagationdelayisapproximatelythesumoftheindividualdelays,aneffectwhichcanbecomeaprobleminhigh-speedcircuits. Logicgatesandhardware[] NANDandNORlogicgatesarethetwopillarsoflogic,inthatallothertypesofBooleanlogicgates(i.e.,AND,OR,NOT,XOR,XNOR)canbecreatedfromasuitablenetworkofjustNANDorjustNORgate(s).Theycanbebuiltfromrelaysortransistors,oranyothertechnologythatcancreateaninverterandatwo-inputANDorORgate. HencetheNANDandNORgatesarecalledtheuniversalgates. Foraninputof2variables,thereare16possiblebooleanalgebraicfunctions.These16functionsareenumeratedbelow,togetherwiththeiroutputsforeachcombinationofinputsvariables. INPUT A 0 0 1 1 B 0 1 0 1 OUTPUT 0 0 0 0 0 AANDB 0 0 0 1 A>B* 0 0 1 0 A 0 0 1 1 AB"is"AdoesnotimplyB".Thesefourfunctionsarelesscommonandareusuallynotimplementeddirectlyaslogicgates. Logicgatesareavitalpartofmanydigitalcircuits,andassuch,everykindisavailableasanIC.Forexamples,seethe4000seriesofCMOSlogicchipsorthe700series. Symbols[] Therearetwosetsofsymbolsincommonuse,bothnowdefinedbyANSI/IEEEStd91-1984anditssupplementANSI/IEEEStd91a-1991.The"distinctiveshape"set,basedontraditionalschematics,isusedforsimpledrawingsandisquickertodrawbyhand.Itissometimesunofficiallydescribedas"military",reflectingitsoriginifnotitsmodernusage.The"rectangularshape"set,basedonIEC60617-12,hasrectangularoutlinesforalltypesofgate,andallowsrepresentationofamuchwiderrangeofdevicesthanispossiblewiththetraditionalsymbols.TheIEC'ssystemhasbeenadoptedbyotherstandards,suchasEN60617-12:1999inEuropeandBSEN60617-12:1999intheUnitedKingdom. Type Distinctiveshape Rectangularshape BooleanalgebrabetweenA&B Truthtable AND INPUT OUTPUT A B AANDB 0 0 0 0 1 0 1 0 0 1 1 1 OR INPUT OUTPUT A B AORB 0 0 0 0 1 1 1 0 1 1 1 1 NOT INPUT OUTPUT A NOTA 0 1 1 0 InelectronicsaNOTgateismorecommonlycalledaninverter.Thecircleonthesymboliscalledabubble,andisgenerallyusedincircuitdiagramstoindicateaninvertedinputoroutput. NAND INPUT OUTPUT A B ANANDB 0 0 1 0 1 1 1 0 1 1 1 0 NOR INPUT OUTPUT A B ANORB 0 0 1 0 1 0 1 0 0 1 1 0 Inpractice,thecheapestgatetomanufactureisusuallytheNANDgate.Additionally,CharlesPeirceshowedthatNANDgatesalone(aswellasNORgatesalone)canbeusedtoreproducealltheotherlogicgates. Symbolically,aNANDgatecanalsobeshownusingtheORshapewithbubblesonitsinputs,andaNORgatecanbeshownasanANDgatewithbubblesonitsinputs.ThisreflectstheequivalencyduetoDeMorganslaw,butitalsoallowsadiagramtobereadmoreeasily,oracircuittobemappedontoavailablephysicalgatesinpackageseasily,sinceanycircuitnodethathasbubblesatbothendscanbereplacedbyasimplebubble-lessconnectionandasuitablechangeofgate.IftheNANDisdrawnasORwithinputbubbles,andaNORasANDwithinputbubbles,thisgatesubstitutionoccursautomaticallyinthediagram(effectively,bubbles"cancel").Thisiscommonlyseeninreallogicdiagrams-thusthereadermustnotgetintothehabitofassociatingtheshapesexclusivelyasORorANDshapes,butalsotakeintoaccountthebubblesatbothinputsandoutputsinordertodeterminethe"true"logicfunctionindicated. Twomoregatesaretheexclusive-ORorXORfunctionanditsinverse,exclusive-NORorXNOR.ThetwoinputExclusive-ORistrueonlywhenthetwoinputvaluesaredifferent,falseiftheyareequal,regardlessofthevalue.Iftherearemorethantwoinputs,thegategeneratesatrueatitsoutputifthenumberoftruesatitsinputisodd([1]).Inpractice,thesegatesarebuiltfromcombinationsofsimplerlogicgates. XOR INPUT OUTPUT A B AXORB 0 0 0 0 1 1 1 0 1 1 1 0 XNOR INPUT OUTPUT A B AXNORB 0 0 1 0 1 0 1 0 0 1 1 1 ListofLogicGateICs[] The7400serieshasseveralICsthatcontainjustfour-inputlogicgates: ICNo. Gate 7400 NAND 7402 NOR 7404 NOT 7408 AND 7432 OR 7486 EX-OR DeMorganequivalentsymbols[] ByuseofDeMorgan'stheorem,anANDgatecanbeturnedintoanORgatebyinvertingthesenseofthelogicatitsinputsandoutputs.Thisleadstoaseparatesetofsymbolswithinvertedinputsandtheoppositecoresymbol.Thesesymbolscanmakecircuitdiagramsforcircuitsusingactivelowsignalsmuchclearerandhelptoshowaccidentalconnectionofanactivehighoutputtoanactivelowinputorvice-versa. Storageofbits8inabyte[] Relatedtotheconceptoflogicgates(andalsobuiltfromthem)istheideaofstoringabitofinformation.Thegatesdiscusseduptoherecannotstoreavalue:whentheinputschange,theoutputsimmediatelyreact.Itispossibletomakeastorageelementeitherthroughacapacitor(whichstoreschargeduetoitsphysicalproperties)orbyfeedback.Connectingtheoutputofagatetotheinputcausesittobeputthroughthelogicagain,andchoosingthefeedbackcorrectlyallowsittobepreservedormodifiedthroughtheuseofotherinputs.Asetofgatesarrangedinthisfashionisknownasa"latch",andmorecomplicateddesignsthatutiliseclocks(signalsthatoscillatewithaknownperiod)andchangeonlyontherisingedgearecallededge-triggered"flip-flops".Thecombinationofmultipleflip-flopsinparallel,tostoreamultiple-bitvalue,isknownasaregister.Whenusinganyofthesegatesetupstheoverallsystemhasmemory;itisthencalledasequentialsystemsinceitsoutputcanbeinfluencedbyitspreviousstate(s). Theseregistersorcapacitor-basedcircuitsareknownascomputermemory.Theyvaryinperformance,basedonfactorsofspeed,complexity,andreliabilityofstorage,andmanydifferenttypesofdesignsareusedbasedontheapplication. Three-statelogicgates[] Three-state,or3-state,logicgateshavethreestatesoftheoutput:high(H),low(L)andhigh-impedance(Z).Thehigh-impedancestateplaysnoroleinthelogic,whichremainsstrictlybinary.Thesedevicesareusedonbusestoallowmultiplechipstosenddata.Agroupofthree-statesdrivingalinewithasuitablecontrolcircuitisbasicallyequivalenttoamultiplexer,whichmaybephysicallydistributedoverseparatedevicesorplug-incards. 'Tri-state',awidely-usedsynonymof'three-state',isatrademarkoftheNationalSemiconductorCorporation. Miscellaneous[] Logiccircuitsincludesuchdevicesasmultiplexers,registers,arithmeticlogicunitarithmeticunits(ALUs),andcomputermemory,allthewayupthroughcompletemicroprocessorswhichcancontainmorethana100milliongates.Inpractice,thegatesaremadefromfieldeffecttransistors(FETs),particularlymetal-oxide-semiconductorFETs(MOSFETs). Inreversiblelogic,Toffoligatesareused. Historyanddevelopment[] Theearliestlogicgatesweremademechanically.CharlesBabbage,around1837,devisedtheAnalyticalEngine.Hislogicgatesreliedonmechanicalgearingtoperformoperations.Electromagneticrelayswerelaterusedforlogicgates.In1891,AlmonStrowgerpatentedadevicecontainingalogicgateswitchcircuit(Template:USpatent).Strowger'spatentwasnotinwidespreaduseuntilthe1920s.Startingin1898,NikolaTeslafiledforpatentsofdevicescontaininglogicgatecircuits(seeListofTeslapatents).Eventually,vacuumtubesreplacedrelaysforlogicoperations.LeeDeForest'smodification,in1907,oftheFlemingvalvecanbeusedasANDlogicgate.LudwigWittgensteinintroducedaversionofthe16-rowtruthtablein#Logicgatesandhardwareabove,asproposition5.101ofTractatusLogico-Philosophicus(1921).ClaudeE.ShannonintroducedtheuseofBooleanalgebraintheanalysisanddesignofswitchingcircuitsin1937.WaltherBothe,inventorofthecoincidencecircuit,gotpartofthe1954NobelPrizeinphysics,forthefirstmodernelectronicANDgatein1924.Activeresearchistakingplaceinmolecularlogicgates. References[] Symbolsforlogicgates.TwentyFirstCenturyBooks,Breckenridge,CO. Tesla'sinventionoftheANDlogicgate.TwentyFirstCenturyBooks,Breckenridge,CO. WirelessRemoteControlandtheElectronicComputerLogiclogicelements "LEGOLogicGates".goldfish.org.uk,2005. Furtherreading[] Awschalom,D.,D.Loss,andN.Samarth,SemiconductorSpintronicsandQuantumComputation(2002),Springer-Verlag,Berlin,Germany. Bostock,Geoff,ProgrammableLogicDevices.TechnologyandApplications(1988),McGraw-Hill,NewYork,NY. Brown,StephenD.etal.,Field-ProgrammableGateArrays(1992),KluwerAcademicPublishers,Boston,MA. Categories: Addcategory Cancel Save CommunitycontentisavailableunderCC-BY-SAunlessotherwisenoted. Advertisement FanFeed 1 XORgate UniversalConquestWiki Let'sGoLuna!Wiki Club57Wiki FollowonIG TikTok JoinFanLab