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thermalconsideration:outputpowerandrecommended
T
一个(最大值)
T
J
θ
JA
P
Dissipated
在哪里 : T
J
125
°
C
θ
JA
1
减额 因素
1
0.01145
87.3
°
C
W
(2)
P
Dissipated
P
o(平均)
1
效率
–1
效率
85% 为 一个 8-
加载
(3)
GAINSETTINGVIAGAIN0ANDGAIN1INPUTS
INPUTRESISTANCE
TPA3007D1
SLOS418A–SEPTEMBER2003–REVISEDDECEMBER2004
AMBIENTTEMPERATURE
tocalculatethemaximumambienttemperature,thefollowingequationmaybeused:
(thederatingfactorforthe24-pinpwpackageisgiveninthedissipationratingtable.)
toestimatethepowerdissipation,thefollowingequationmaybeused:
例子.whatisthemaximumambienttemperatureforanapplicationthatrequiresthetpa3007d1todrive3
wintoan8-
Ω
扬声器?
P
Dissipated
=3wx((1/0.85)-1)=0.529w
T
Amax
=125
°
c-(87.3
°
c/wx0.529w)=78.8
°
C
thiscalculationshowsthatthetpa3007d1candrive3wintoan8-
Ω
speakeruptotheabsolutemaximum
ambienttemperatureratingof78.8
°
c,whichmustneverbeexceeded.
thegainofthetpa3007d1issetbytwoinputterminals,gain0andgain1.
thegainslistedintable2arerealizedbychangingthetapsontheinputresistorsinsidetheamplifier.这个
causestheinputimpedance(z
i
)tobedependentonthegainsetting.theactualgainsettingsarecontrolledby
ratiosofresistors,sothegainvariationfrompart-至-partissmall.不管怎样,theinputimpedancemayshiftby
30%duetoshiftsintheactualresistanceoftheinputresistors.
fordesignpurposes,theinputnetwork(discussedinthenextsection)shouldbedesignedassuminganinput
impedanceof23k
Ω
,whichistheabsoluteminimuminputimpedanceofthetpa3007d1.atthelowergain
settings,theinputimpedancecouldincreaseashighas313k
Ω
.
table2.gainsettings
AMPLIFIERGAININPUTIMPEDANCE
(db)(k
Ω
)
GAIN1GAIN0
TYPTYP
0012241
0118168
1023.6104
113633
eachgainsettingisachievedbyvaryingtheinputresistanceoftheamplifier,whichcanrangefromitssmallest
valuetooversixtimesthatvalue.asaresult,ifasinglecapacitorisusedintheinputhigh-passfilter,这-3db
orcutofffrequencyalsochangesbyoversixtimes.
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