Datasheet
_
+
V
DD
V
O+
V
O-
GND
ToBattery
C
s
Bias
Circuitry
IN-
IN+
SHUTDOWN
R
I1
R
F
C
I1
C
P
R
P
R
F
C
( )
BYPASS
(Optional)
C
I2
R
I2
SingleEnded
Input1
SingleEnded
Input2
InputCapacitor(C
I
)
SELECTINGCOMPONENTS
Resistors(R
F
andR
I
)
Gain − R
F
/R
I
(1)
f
c
+
1
2pR
I
C
I
(2)
BypassCapacitor(C
BYPASS
)andStart-UpTime
–3 dB
f
c
C
I
+
1
2pR
I
f
c
(3)
TPA6205A1
www.ti.com
..............................................................................................................................................................SLOS490B–JULY2006–REVISEDJUNE2008
Figure31.ApplicationSchematicWithTPA6205A1SummingTwoSingle-EndedInputs
TheTPA6205A1doesnotrequireinputcoupling
capacitorsifusingadifferentialinputsourcethatis
biasedfrom0.5VtoV
DD
-0.8V.Use1%tolerance
Theinput(R
I
)andfeedbackresistors(R
F
)setthe
orbettergain-settingresistorsifnotusinginput
gainoftheamplifieraccordingtoEquation1.
couplingcapacitors.
Inthesingle-endedinputapplicationaninput
R
F
andR
I
shouldrangefrom1kΩto100kΩ.Most
capacitor,C
I
,isrequiredtoallowtheamplifiertobias
graphsweretakenwithR
F
=R
I
=20kΩ.
theinputsignaltotheproperdclevel.Inthiscase,C
I
andR
I
formahigh-passfilterwiththecorner
Resistormatchingisveryimportantinfullydifferential
frequencydeterminedinEquation2.
amplifiers.Thebalanceoftheoutputonthereference
voltagedependsonmatchedratiosoftheresistors.
CMRR,PSRR,andthecancellationofthesecond
harmonicdistortiondiminishesifresistormismatch
occurs.Therefore,itisrecommendedtouse1%
toleranceresistorsorbettertokeeptheperformance
optimized.
TheinternalvoltagedividerattheBYPASSpinofthis
devicesetsamid-supplyvoltageforinternal
referencesandsetstheoutputcommonmode
voltagetoV
DD
/2.Addingacapacitortothispinfilters
anynoiseintothispinandincreasesthek
SVR
.
C
(BYPASS)
alsodeterminestherisetimeofV
O+
andV
O-
whenthedeviceistakenoutofshutdown.Thelarger
thecapacitor,theslowertherisetime.Althoughthe
ThevalueofC
I
isimportanttoconsiderasitdirectly
outputrisetimedependsonthebypasscapacitor
affectsthebass(lowfrequency)performanceofthe
value,thedevicepassesaudio4µsaftertakenoutof
circuit.ConsidertheexamplewhereR
I
is10kΩand
shutdownandthegainisslowlyrampedupbasedon
thespecificationcallsforaflatbassresponsedown
C
(BYPASS)
.
to100Hz.Equation2isreconfiguredasEquation3.
Tominimizepopsandclicks,designthecircuitsothe
impedance(resistanceandcapacitance)detectedby
bothinputs,IN+andIN-,isequal.
Inthisexample,C
I
is0.16µF,soonewouldlikely
chooseavalueintherangeof0.22µFto0.47µF.A
furtherconsiderationforthiscapacitoristheleakage
pathfromtheinputsourcethroughtheinputnetwork
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