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3.4.1UnityGainOutput
3.4.2OutputGainof2
EVMOperation
ThebufferedoutputconfigurationcanbeusedtopreventloadingoftheDAC8555,thoughitmayadd
someslightdistortionbecauseofthefeedbackresistorandcapacitor.Thefeedbackcircuitcanbealtered
bysimplydesolderingR8andC12andreplacingthemwithcomponentsofdesiredvalue.Ifdesired,R8
andC12canberemovedaltogetherbyreplacingR8witha0Ωresistor.
Table4showsthejumpersettingfortheunitygainconfigurationoftheDACexternaloutputbufferin
unipolarorbipolarmode.
Table4.UnityGainOutputJumperSettings
JumperSetting
ReferenceUnipolarBipolarFunction
JMP5OpenOpenDisconnectV
REF
Hfromtheinvertinginputoftheopamp.
JMP102-31-2SuppliesV
SS
tothenegativerailoftheopamportiesittoAGND.
JMP6OpenOpenDisconnectnegativeinputofopampfromthegainresistor,R9.
Therearetwotypesofconfigurationsthatwillyieldanoutputgainof2,dependingonthesetupofjumpers
JMP5andJMP6.TheseconfigurationsallowtheusertochoosewhethertheDACoutputwilluseV
REF
H
asanoffset.Table5showstheproperjumpersettingsoftheEVMfortheDAC8555outputgainof2.
Table5.OutputGainof2JumperSettings
JumperSetting
ReferenceUnipolarBipolarFunction
InvertinginputoftheoutputopampU2isconnectedtoV
REF
Hforuseasitsoffset
CloseClose
voltagewithagainof2.JMP6mustbeopen.
JMP5
V
REF
HisdisconnectedfromtheinvertinginputoftheoutputopampU2.JMP6mustbe
OpenOpen
closed.
Suppliespower,V
SS
,tothenegativerailofopampU2forbipolarmode,ortiesitto
JMP102-31-2
AGNDforunipolarmode.
ConfiguresopampU2foragainof2outputwithoutavoltageoffset.JMP5mustbe
CloseClose
open.
JMP6
InvertinginputofopampU2isdisconnectedfromthegainresistor,R9.JMP5mustbe
OpenOpen
closed.
DAC8555EVMUser'sGuide 18SLAU204–December2006
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