www.德州仪器.com
R
L
C
C
V
o(pp)
V
o(pp)
V
DD
-3 db
f
c
V
(lrms)
V
O
I
DD
I
dd(avg)
FULLYDIFFERENTIALAMPLIFIER
TPA6211A1
SLOS367B–AUGUST2003–REVISEDAUGUST2004
aneasy-至-useequationtocalculateefficiencystarts
outasbeingequaltotheratioofpowerfromthe
powersupplytothepowerdeliveredtotheload.至
accuratelycalculatetheRMSandaveragevaluesof
powerintheloadandintheamplifier,thecurrentand
voltagewaveformshapesmustfirstbeunderstood
(seefigure35).
figure34.单独的-endedoutputandfrequency
回馈
figure35.voltageandcurrentwaveformsfor
Increasingpowertotheloaddoescarryapenaltyof
BTLAmplifiers
increasedinternalpowerdissipation.theincreased
dissipationisunderstandableconsideringthatthe
AlthoughthevoltagesandcurrentsforSEandBTL
BTLconfigurationproduces4
×
theoutputpowerof
aresinusoidalintheload,currentsfromthesupply
theseconfiguration.
aredifferentbetweenseandbtlconfigurations.在
anSEapplicationthecurrentwaveformisa
half-waverectifiedshape,whereasinbtlitisa
EFFICIENCYANDTHERMALINFORMATION
全部-waverectifiedwaveform.thismeansrmscon-
versionfactorsaredifferent.keepinmindthatfor
类-abamplifiersareinefficient,primarilybecause
mostofthewaveformboththepushandpulltransis-
ofvoltagedropacrosstheoutput-stagetransistors.
torsarenotonatthesametime,whichsupportsthe
Thetwocomponentsofthisinternalvoltagedropare
factthateachamplifierintheBTLdeviceonlydraws
theheadroomordcvoltagedropthatvariesinversely
currentfromthesupplyforhalfthewaveform.这
tooutputpower,andthesinewavenatureofthe
followingequationsarethebasisforcalculating
输出.thetotalvoltagedropcanbecalculatedby
amplifierefficiency.
subtractingtheRMSvalueoftheoutputvoltagefrom
V
DD
.theinternalvoltagedropmultipliedbythe
averagevalueofthesupplycurrent,i
DD
(avg),deter-
minestheinternalpowerdissipationoftheamplifier.
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