www.德州仪器.com
powersupplydecoupling,c
(s)
midrailbypasscapacitor,c
(byp)
outputcouplingcapacitor,c
(c)
f
c(高)
1
2
R
L
C
(c)
−3 db
f
c
(4)
TPA6011A4
SLOS392A–FEBRUARY2002–REVISEDJULY2004
thetpa6011a4isahigh-performancecmosaudioamplifierthatrequiresadequatepowersupplydecouplingto
ensuretheoutputtotalharmonicdistortion(thd)isaslowaspossible.powersupplydecouplingalsoprevents
oscillationsforlongleadlengthsbetweentheamplifierandthespeaker.theoptimumdecouplingisachievedby
usingtwocapacitorsofdifferenttypesthattargetdifferenttypesofnoiseonthepowersupplyleads.forhigher
frequencytransients,尖刺,ordigitalhashontheline,agoodlowequivalent-序列-阻抗(等效串联电阻)陶瓷的
电容,typically0.1µfplacedascloseaspossibletothedevicev
DD
含铅的,worksbest.forfiltering
更小的-frequencynoisesignals,alargeraluminumelectrolyticcapacitorof10µforgreaterplacedneartheaudio
poweramplifierisrecommended.
themidrailbypasscapacitor(c
(byp)
)isthemostcriticalcapacitorandservesseveralimportantfunctions.在
开始-uporrecoveryfromshutdownmode,c
(byp)
determinestherateatwhichtheamplifierstartsup.thesecond
functionistoreducenoiseproducedbythepowersupplycausedbycouplingintotheoutputdrivesignal.这个
noiseisfromthemidrailgenerationcircuitinternaltotheamplifier,whichappearsasdegradedpsrrand
thd+n.
bypasscapacitor(c
(byp)
)valuesof0.47-µfto1-µfceramicortantalumlow-esrcapacitorsarerecommended
forthebestthdandnoiseperformance.forthebestpopperformance,chooseavalueforc
(byp)
thatisequalto
orgreaterthanthevaluechosenforC
i
.thisensuresthattheinputcapacitorsarechargeduptothemidrail
voltagebeforeC
(byp)
isfullychargedtothemidrailvoltage.
inthetypicalsingle-supplyseconfiguration,anoutputcouplingcapacitor(c
(c)
)isrequiredtoblockthedcbiasat
theoutputoftheamplifier,thuspreventingdccurrentsintheload.aswiththeinputcouplingcapacitor,这
outputcouplingcapacitorandimpedanceoftheloadformahigh-passfiltergovernedbyequation4.
themaindisadvantage,fromaperformancestandpoint,istheloadimpedancesaretypicallysmall,whichdrives
thelow-frequencycornerhigher,degradingthebassresponse.largevaluesofc
(c)
arerequiredtopasslow
frequenciesintotheload.considertheexamplewhereac
(c)
of330µFischosenandloadsvaryfrom3
Ω
,4
Ω
,
8
Ω
,32
Ω
,10k
Ω
,and47k
Ω
.table4summarizesthefrequencyresponsecharacteristicsofeachconfiguration.
table4.commonloadimpedancesvslowfrequency
OutputCharacteristicsinSEMode
最低
R
L
C
(c)
频率
3
Ω
330µF161Hz
4
Ω
330µF120Hz
8
Ω
330µF60Hz
32
Ω
330µF15Hz
10,000
Ω
330µf0.05hz
47,000
Ω
330µf0.01hz
23
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