What is NOT Gate : Working & Its Applications

NOT gate is also called an inverter gate where it inverts the input signal that is applied to it. This is the single input and single output ... Youarehere:Home/DigitalElectronics/WhatisNOTGate:Working&ItsApplicationsInanyofthedigitalcircuits,theprimarydevicethatholdsmoreprominenceisthelogicgate.Thenamelogicgatescomefromthecapabilityofthosedevicestoprovideoutputsdependingonmultiplecombinationsofinputs.Theselogicgatesaremainlycategorizedasbasiclogicgates,specialpurpose,anduniversalgates.TheonebasicgatewhichwearegoingtodiscusstodayisNOTgate.TheinventorofNOTgatewasGeorgeBooleandhealsoinventedtheconceptofbooleanlogic.Today,thisarticlehelpsusinknowingthefunctionalityoftheinverter,itscircuit,design,applications,benefits,andlimitations.WhatisNOTGate?NOTgateisalsocalledaninvertergatewhereitinvertstheinputsignalthatisappliedtoit.Thisisthesingleinputandsingleoutputgate.Here,inversioncorrespondsthatlogic‘0’tobeconvertedintologic‘1’andlogic‘1’convertedtologic‘0’.TheNOTgatesymbolisintheformthatithasatrianglehavingabubbleattheend.Thisbubbleistermedaninversionbubblewhichprovidesthecomplementedsignalofinput.Thisgateisalsocalledadecision-makinggateduetothereasonthatithasonlysingleinput.Inthisinverterlogicgate,thebubblecanalsobepresentontheinputsideofthegatewhichrepresentsanactivelessinputsignal.Thisinversionoftheinputintheinverterisnotjustboundtothegate,itcanevenbeimplementedforanyothergatesorinmanydigitalcircuits,andeitheritcanbeatinputoroutputsignal.Forexample,whentheinputsignalisconsideredasX,thentheoutputoftheinvertergateisX’.Similarlywhenthevalueoftheinputsignalis‘1’,thentheoutputis‘0’andviceversa.TheNOTgatesymbolisshownbelow:SymbolofNOTgateAstruthtablelistsouttheoutputsforallthecombinationsofappliedinputsignals.BelowistheNOTgatetruthtableInputOutputX=0X’=1X=1X’=0ThefunctionalitycanbeclearlyexplainedwiththebelowNOTgatecircuitdiagram.SymbolofinvertergateThepictureshowsthattheLEDdevicewillglowwhenswitchSisinanOPENstateanditmovestoOFFwhenswitchSisintheCLOSEDstate.NOTGateusingTransistorTheNOTlogicgatecanbeeasilyimplementedthroughthebipolartransistor.Belowisthediagramthatshowsinverterimplementationusingatransistor.NOTGateUsingTransistorCase1:WhenhighvoltageisappliedasinputtotheinverterwhichisVcc=+5V.Here,thetransistorTxreceivestherequiredamountofpotentialtomoveintoONcondition.WhenthetransistormovesintotheONstate,thevoltageatBterminalwillhaveapathtotheearthviaresistorR1.Now,thetransistorwillbeinshort-circuitedcondition,sothatalltheVccvoltagegetsdroppedatR1andnovoltageappearsattheoutputterminalwhichisideally‘0’volts.Ingeneral,therehappenssomeamountofvoltagedropattheemitterandcollectorterminalswhichisapproximately0.6V. So,theentiresupplyvoltagewillnotbedroppedattheresistoritis5-0.6=4.4Volts.Sothat0.6Visalmostconsideredas‘0’orlogic‘0’.Case2:Whenalowvoltage(0V)isappliedasinputtotheinverterthenthetransistor’sbaseterminalisprovidedwith0Voritisgrounded.Now,thetransistorTxmovesintoOFFconditionandthesupplyvoltagehasnopathtomovetoearthandtheentirevoltagewillbeattheoutputterminalwhichmeansthattheoutputisatlogicHIGH.NotUsingNANDGateToderiveinvertercircuitfromNAND,ithastobeconsideredthatboththeinputsoftheNANDgateareconnectedwhichistakenasasingleinputtotheNANDgate.Withthisconnection,whentheinputwaspassedthroughtwo-inputNANDgates,thenitresultsinacomplementoftheinputsignal.ThisrepresentsalogicalnegationoftheinputwhichistheoperationofNOTgate.BelowisthelogicaldiagramthatshowsanimplementationofaninvertercircuitusingNANDgate.NOTUsingNANDAspertheIdempotencyprinciple,(X.X)’=(X)’So,(X.X)’=X’NOTLogicGateusingNORGateToderiveNOTgateusingNOR,ithastobeconsideredthatboththeinputsofNORgateareconnectedwhichistakenasasingleinputtoNORgatebecauseNOThasasingleinput.Here,theIC7402isusedwhichisaquad2-inputNORgate.So,whenabinaryHIGHinputisgivenasinput,theresultislogicLOWandinthesameway,whenabinaryLOWsignalisprovidedasinput,theoutputislogicHIGH.NOTUsingNORInverterusingMultiplexerToimplementNOTgateusingmux,theonlythingtodoistheenabletheinvertingpath.ThishappenswhentheA0pininthemuxisconnectedto1andtheA1pinisconnectedto0.Itcanalsobesaidthatthesignal‘0’hastobepropagatedtooutputwhentheinputsignalis‘1’andsignal‘1’hastobepropagatedtooutputwhentheinputsignalis‘0’.ThebelowdiagramshowstheimplementationofNOTgateusingmux.SY0110NOTUsingMultiplexerY=S’A0+SA1=S’.1+S.0Y=S’ NOTGateInverterICTheICnumberfortheinverterdeviceis7404whichisahigh-speedCMOStechnologyquadinputone.ThisICconsistsof6individualNOTgateswhichallareconsideredassinglepackages.ThisICistermedahexinverterbecauseitcontains6separateinvertersandtheoutputsaredirectlyinterfacedtoTTL,NMOS,andCMOS.IC7404ThevoltagelevelsrequiredforNOTgateICare:ThesupplyvoltageVccrangesbetween4.75to5.25voltsandthenominalvoltagerangeis5V.TheminimumlevelofHIGHinputvoltageVIHis2VThemaximumlevelofLOWinputvoltageVILis0.8VThemaximumlevelofHIGHoutputcurrentIOHis-0.4mAmpsTheminimumlevelofLOWoutputcurrentIOLis16mAmpsThepindescriptionof7404NOTgateICisInputterminals1–Inputofgate13–Inputofgate25–Inputofgate39–Inputofgate411–Inputofgate513–Inputofgate6Outputterminals2–outputofgate14–outputofgate26–outputofgate38–outputofgate410–outputofgate512–outputofgate6Commonterminals7–groundpinwhichisconnectedtoground14–VccpinwhichsuppliespositivevoltagetotheICVHDLCodeofInverterThissectionexplainstheimplementationofNOTgateinaVHDLcodeStep1:Initially,thelibrariesareimportedStep2:ThentheentityisstatedasNOTgateandalsoinputandoutputsaredeclaredasXandYStep3:Afterthedeclarationoftheentity,thearchitectureofthedeclaredentityhastobedefined.Here,thearchitectureofNOTgateentityisgivenas“architecturenotLogicofNOT”.AsweknowYisconsideredasoutputwhichisnothingbutNOTfunctionalityforinputX. So,YismappedwithXwhichisY<=NOT(X).Thenthearchitectureisclosedby“endnotLogic”.TheVHDLcodeimplementationofNOTgateis:libraryIEEE;useIEEE.std_logic_1164.all;entityNOTisport(X:instd_logic;Y:outstd_logic               );endNOT;architecturenotLogicofNOTisbeginY<=not(X);endnotLogic;ElectronicExecutionofInverterLogicGateTheinvertercircuitscanevenbeimplementedthroughNMOS,andPMOStransistorscoupledwithresistorcomponents.Astheresistivedraintechniquesuseonlyonetransistor,theNOTgatedesigncanalsobedoneatminimalprices.Thoughtheflowofcurrentintheresistorhappensintwostates,thisresistivedraintechniqueisnotimplementedforhighprocessingspeedsandutilizesmorepower.Asanalternative,invertersaredesignedwiththehelpofcomplementaryconfigurationsintheCMOStechnology.Withthisconfiguration,powerusagecanbereducedbecauseonetransistorwillbealwaysintheOFFstateinboththelogicstates.TheprocessingspeedcanbeenhancedbecauseofcomparativelylessresistancewhencomparedwiththeonlyNMOSoronlyPMOSapproaches.ThesegatescanalsobedesignedusingBJTdeviceseitherinTTLorRTLconfigurations.ThebelowpictureshowstheimplementationoftheinverterinNMOS,PMOS,staticCMOS,NPNRTL,andNPNTTLconfigurations.NOTGateinVariousConfigurationsTheanalyticalillustrationofinvertercanbegivenas:f(x)=1–xwheref(0)=1–0=1f(1)=1–1=0HexInverterBasedontheabovediscussion,wecametoknowthataninvertercircuitcanalsobedesignedthroughatransistor.WhereastransistorsrequiresomeamountoftimeforswitchingbetweenONandOFFstates.Theswitchingphenomenontakesplacewithsomehold-uptimeinthetransistorsandthisdoesnothappeninstantly.Also,thetransistorholdstheforemostfeatureofamplificationthatdirectstoitsfunctionalityinthismode.Inthelinearamplificationfunctionality,a minimalvariationintheinputcorrespondstothecorrespondingvariationintheoutputandthisalsoleadstoswitchingbetweenONandOFFstatessuddenly.Inordertogetridofthesecomplications,aHexorSchmittinverterisdesigned.Asweknow,intheTTLconfiguration, 2– 5voltsistakenasHIGHlogicand0–0.8voltsistakenasLOWlogic.Here,2voltsand0.8voltsaresettobeUpperandLowerThresholdVoltagelevels(UTVandLTV).ThefunctionalityoftheSchmittinvertertakesplacebasedonthelimitsofUTVandLTVandvariesitsstateabruptly.WhenthereisariseintheinputvoltagemorethantheUTVlevel,thentheoutputoftheSchmittinverteralterstoLOWlogicandinthesamewaywhenthereisadropintheinputvoltagebelowtheLTVlevel,thentheoutputoftheSchmittinverteralterstoHIGHlogic.SchmittInverterThisholdstheprecedingstateatthetimeofthetransitionperiodandvariesitsstatequicklywhenthethresholdvoltageisreached.ThisistermedHysteresiswhichisinbuiltintheSchmittinverter.ThepictorialrepresentationofUTVandLTVlimitsalongwiththeoutputwaveformisshownbelow:PerformanceAnalysisTheperformanceoftheinvertercircuitiscalculatedthroughavoltagetransfercurvewherethecurveisplottedagainstinputandoutputvoltages.WiththisVTCcurve,theparameterslikefunctionallogiclevels,gain,noiselevelscanalsobemeasured.VTCCurveofInverterMostly,theVTCcurveappearsasaninvertedstepfunctionwherethisrepresentstheexactswitchingofOFFandONstates,whereasintherealscenarioasteadytransitionlocationalsoexists.TheVTCcurverepresentsthatforminimalvoltagelevels,theoutputishighandviceversa.Thetransitionintheslopeisconsideredaqualitymeasurement.Andwhenitissteep,itresultsinexactswitchingmeasurement.ThenoisetolerancecanevenbecalculatedbyrelatingtheminimumandmaximumlevelsofinputandoutputforeveryfunctionalregionofONandOFF.ApplicationsTheforemostNOTgateapplicationisintheCMOSinverterforthegenerationofwaveforms.Employedintemperaturedetectiondevices.Usedindailyusagedeviceslikedesktops,tablets,andmobiles.Complexdevicessuchasdecoders,statemachines,andmultiplexersalsouseinvertercircuits.Usedinacrystaloscillator.NOTGateAdvantagesandDisadvantagesThebenefitsare:Inverterdevicescanbeconstructedatalowcost.Requiresminimalpowerconsumptionforitsoperation.Enhancedprocessingspeed.CanbeconstructedinRTLandTTLconfigurationsThedrawbacksare:IthasanonlysingleoutputandisnotsuitablefortherequirementofprovidingtwoinputsThereisthelimitedoperationalvoltagelevelPleaserefertothislinktoknowmoreaboutOpenDrain.And,thisisthedetailedinformationofNOTgate.Thisarticlehasprovidedaclearoverviewondefininginverter,truthtable,circuit,implementationusingmux,benefits,anddrawbacks.Know,howaninverterisusedinacrystaloscillatordevice?RecentPostsWhatisInter-ProcessCommunication:Working,Types&ItsApplicationsWhatisClassDAmplifier:Working,Types,Characteristics&BenefitsMQ2ArduinoGasSensor:PinConfiguration&ItsWorkingWhatisDMAController:Working&ItsApplicationsWhatisLowNoiseAmplifier:Working,Types,Design&ItsApplicationsWhatisAVRMicrocontroller:PinOut,Working&ItsApplicationsWhatisI3CProtocol:Working&ItsApplicationsWhatisIEEE488BusorGPIB:Working&ItsApplicationsWhatisAntennaArray:Architecture&ItsApplicationsWhatisDigitalPotentiometer:Working&ItsApplicationsWhatisYagiUdaAntenna:Design,Working&ItsApplicationsWhatisPreprocessor:Definition,Syntax&ItsCommandsCategoriesArticles(20)Basics(112)Communications(53)Components(39)DigitalElectronics(41)DigitalSignalling(3)Electronics(170)EmbeddedSystems(11)Magnetism(5)Microprocessors(3)Modulation(1)Projects(15)SubscribetoOurNewsletterPleaseleavethisfieldemptyDon’tmissthesearticles!Wedon’tspam!Readourprivacypolicyformoreinfo.Checkyourinboxorspamfoldertoconfirmyoursubscription.CategoryMostReadABOUTContactUsPrivacyPolicy