Investigating Sensor Signal and Amplifier1文档格式.docx
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Investigating Sensor Signal and Amplifier1文档格式.docx
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(decibel)tothat.Gainpoweramplifieroutputwiththeinputsignalfrequencychangesintheupgradeorattenuation.Thisindicatorisapoweramplifierqualityassessmentofthemostimportantadvantagesanddisadvantagesofabasis.ThesmallerthevalueofthedBonthepoweramplifiermoreflatfrequencyresponsecurve,thesmallerthedistortion,thesignalreductionandthestrongertheabilitytoreproduce.
Whenconsideringasignalthanthereferencesignalwhenthelargenumberoftimes,wesaythatasignalonthenumberofreferencesignalgain,isthe"
recordedas"
iscalculated:
(ZichengChen,2008)
Gain(dB)=10×
log(targetsignalpower/referencesignalpower)
Forexample,inapowercircuittobeenlargedto100mWpower1000mW,thisclassisthegainofcircuit10×
log(1000/100)=100dB.Onceagainreminded,amplifiergainisnottoenlargetheenergyofthesignalitself,butthepoweroftheenergytransformedintothesignal.ThesignalcircuitsbecomesmallerwhencalculateddBgainisnegative.
Whenconsideringmorethanasignaltoreducetheproportionofthebaselinesignal,wesaythatasignalofthebaselinenumberofsignalattenuation(attenuation),unitis"
Attenuation(dB)=10×
log(referencesignalpower/objectsignalpower)
Forexample,aUHFbandofamateurradioantennausedistoolong,toosmallandpoorqualitycable,transmitteroutputpowerof20Wtoreachonly2Wantenna,thesignalinthecable'
sattenuationis10×
log(20/2)=10dB.Attenuationoftheenergyoutcableisnot"
eating"
lost,butbecauseoftheheatconductorordielectric,theRFenergyintoheat,radiationorconductiontothesurroundingair.
WhenthecircuitsothatthesignalincreasedwhencalculatedattenuationdBisnegative.
Therefore,wecaninterpretitthiswayonthegainandattenuationofthebasiccalculation:
Asetofmultiplesneedtoenlarge
A=10x
XDBforgainorattenuation
Gain/attenuation=log10X=XDB
WhenA>
1,theamplifierthatisAtimes,thatis,X>
0at
ThistimeforthegainofamplifierXDB.
WhenA<
1whenX<
0atthistimefortheattenuationofamplifierXDB.
(Shengxiefy,2008)
"
Noise"
isusuallyusedtodescribethebroadrequirementsthatwouldhaveadistortionofthesignalpurityoftheextraelectricalsignal.Sometype(types)ofnoiseis(are)unavoidable(forexample,measuredtheactualsignalamplitudefluctuations),onlythroughthesignalbandwidthoftheaveragesystolicandtechnologytoovercomesuchnoise.Anothertypeofnoise(forexample,radiofrequencyinterferenceandthe"
groundloop"
)throughdifferenttechnologiestoreduceoreliminate,includingfilteringtechnologyandcarefullocationofconnectionsettingsanddisplaydevices.Finally,thereisanoise,itscausesandintheprocessofsignalamplificationbylownoiseamplifierdesigntechniquestoweaken.Althoughnoisereductiontechniquesareeffective,but(删掉)alwayswanttobefreefromnoiseandhavethelowestpossiblenoiseamplifierusingnoisereductionsystem.Electroniccircuitsisnoiseamplifierorelectronicequipmentwithausefuloutputsignal,atthesametimethereisarandomchangeinthecurrentorvoltagesignalisnotusefulwhenitexists.Hereistheimpactofthevarioustypesofelectroniccircuitsasimplesummaryofthenoise.(xiaofengqi,yizhang,2001)
Circuitnoise(amplifiernoise):
referstotheinternalamplifiernoisesourcesandcharacteristicsoftheinternalnoiseamplifierincludinginputchangecomesmainlyfromtheresistance,includingthermalnoiseandamplifiernoisepieces.
Resistivityofthethermalnoise
Resistanceintheabsenceofanappliedvoltage,theresistanceofmaterialstomakethefree-electronerraticmovement,amovementhe(it)wouldhaveverylittleresistanceatbothendsofthevoltage,overaperiodoftime,appearthesameastheprobabilityofpositiveandnegativevoltage,thustheaveragevoltageatbothendsto0.However,atransient,thevoltageresistanceofthesizeanddirectionofchangeisrandom.Thermalnoise(alsoknownasJohnsonorwhitenoise)isthat,withthetemperatureandtheheatcausedbytheinteractionoffreeelectronandionvibrationconductor.Itsfrequencycontentisspreadequallythroughouttheband.
ResistancefortheresistorRatbothendsofthethermalnoisevoltageofapositiveGaussiandistribution,itsmeanis0,theunilateralpowerspectraldensityfor:
k=Boltzmann'
sconstant(1.38*10^-23J/K)
T=resistortemperatureinKelvin(T=273+temperatureinCelsius)
BW=frequencybandwidthofthesystembeingconsidered
ShotNoise
AsaresultofminoritycarrierbytheemitterintothebasethroughthePNjunctionareainunittimeinjectedintothecarrierthenumberofdifferent,randomupsanddowns.Suchfluctuationswillaffectthecollectorcurrentoftheupsanddowns;
theresultingnoiseiscalledshotnoise.
I=(2q*Idc*BW)^1/2
i=shotnoise(RMSamperes)
q=electroncharge(Coulombs)
Idc=DCcurrent(A)
BW=bandwidth(Hz)
I^2=2qID*△f
Forallotherdevices,suchastransistors,novalidformulaisavailable.Seethedevicemanufacturer'
sdatasheet.Shotnoiseandthermalnoiseareadditive.
3.3.Scintillationnoise
Flickernoise,alsoknownas1/fnoise.Itismainlyinthelow-frequency(afewthousandHzorless)playamajorroleinthescope.Thisnoisecauses(causedby)theproductionofsemiconductormaterialsandwhenhandlingandcleaningthesurfaceoftheappliedvoltage,inthehigh-frequencyworkdonotusuallyconsiders(usuallydon’tconsider)theimpact(effect)ofit.
V2=k*Idc/f
Acomponent'
snoisecontributionisdeterminedbyitsSPICEmodel.Withinthemodeltwoparameterswillaffecttheoutputofthenoiseanalysis:
AF=Flickernoisecomponent(AF=0)
KF=FlickerNoise(KF=1).
Theimpact(effect)ofnoiseonthecircuit:
Withtheelectronicequipmentofhigh-densityapplications(Withhigh-densityapplicationoftheelectronicequipment),theelectromagneticfieldgeneratedbytheinterferencewouldnotonlyimpedesignaltransmission,butalsodangerous.Itdidnotprocessanalogcircuits,thefunctionaldesignstagesofthecircuithavebeenidentified,theoutputfromtheinputsignalanddeterminedthefunctionofdesign.Anddigitalcircuitoutputfromtheinputsignalanddeterminedthefunctionofdesign.Anddigitalcircuitoutputisnotonlydecidedbythecircuit,butalsotheinputsignalbytheproceduresanddecisionsandwiththecurrentandpastsignals.Digitalcircuitnoiseintrusionoftentriggerchangesinarow,suchasactionstochangestoragememoryandcontinuestothischangeprocess,thecircuitorequipmentwillbelossofnormalfunction.Electromagneticradiation,usuallyinthesignal,theradarsignalsandcommunicationssignalsandothertypesofsignalsmixedwithnoisesuppressionandthereforewheretodistinguishsignalfromnoiseisallthemoreimportant.Tonenoiseisgenerallythedifferencebetweennoises,oftencalledtheelectromagneticnoisetothenoiseofthecircuitarealsoelectromagneticnoiseimpact.(YuSun,2007)
Ascanbeseenfromthegraph,thenoiseinanalogcircuitscannotbeneglected;
Noiseisanelectronicsignal,whichmeanssomesortofinterferenceeffect,isduetothereasonsforthecircuitnoisecausedbyabadreaction.Andthepresenceofcircuitnoise,interferenceisnotnecessarilythere.Inthedigitalcircuit,Oscilloscopescanbeusedisoftenobserved(toobserve)inthenormalpulsesignalonamixtureofsomesmallpeakpulseisnotdesired,butanoise.However,duetotherelationshipbetweencircuitproperties,whicharestillnotinasmallpeakpulselogicdigitalcircuitcausedbytheconfusion,soitcanbesatisfiedthatthereisnointerference.Whennoisevoltageslargehaveenoughpowertomakethecircuitsusceptibletointerference,thenoisevoltageiscalledtheinterferencevoltage.Andacircuitoradevice,whenitcanto(删掉)maintainnormalworkinghoursbythelargestincreaseinnoisevoltage,(删掉逗号)isreferredtoasthecircuitordevice,ortoleranceofanti-interferenceimmunity.Ingeneral(Ingeneralspeaking),itisdifficulttoeliminatenoise,soweinthedesignof(sowhenwedesigethe)analogcircuits,itshouldbetotakeintoaccounttheimpact(effect)ofnoiseforthecircuit,itisnecessarytotrytoreducenoiseorincreasetheintensityoftheimmunitycircuitsot
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