LMH6628 Dual Wideband, Low Noise, Voltage Feedback Op Amp
Literature Number: SNOSA02C
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LMH6628DualWideband,LowNoise,VoltageFeedbackOpAmpMay2005
LMH6628
DualWideband,LowNoise,VoltageFeedbackOpAmp
GeneralDescription
TheNationalLMH6628isahighspeeddualopampthatoffersatraditionalvoltagefeedbacktopologyfeaturingunitygainstabilityandslewenhancedcircuitry.TheLMH6628’slownoiseandverylowharmonicdistortioncombinetoformawidedynamicrangeopampthatoperatesfromasingle(5Vto12V)ordual(±5V)powersupply.
EachoftheLMH6628’scloselymatchedchannelsprovidesa300MHzunitygainbandwidthandlowinputvoltagenoise
).Low2nd/3rdharmonicdistortion(−65/density(2nV/
−74dBcat10MHz)maketheLMH6628aperfectwidedy-namicrangeamplifierformatchedI/Qchannels.
Withitsfastandaccuratesettling(12nsto0.1%),theLMH6628isalsoanexcellentchoiceforwidedynamicrange,anti-aliasingfilterstobuffertheinputsofhiresolutionanalog-to-digitalconverters.CombiningtheLMH6628’stwotightlymatchedamplifiersinasingle8-pinSOICpackagereducescostandboardspaceformanycompositeamplifierapplicationssuchasactivefilters,differentiallinedrivers/receivers,fastpeakdetectorsandinstrumentationamplifi-ers.
TheLMH6628isfabricatedusingNational’sVIP10™com-plimentarybipolarprocess.
Toreducedesigntimesandassistinboardlayout,theLMH6628issupportedbyanevaluationboard(CLC730036).
Features
nnnnnnn
Wideunitygainbandwidth:300MHzLownoise:2nV/
LowDistortion:−65/−74dBc(10MHz)Settlingtime:12nsto0.1%
Widesupplyvoltagerange:±2.5Vto±6VHighoutputcurrent:±85mA
ImprovedreplacementforCLC428
Applications
nnnnnn
HighspeeddualopampLownoiseintegratorsLownoiseactivefilters
Driver/receiverfortransmissionsystemsHighspeeddetectorsI/Qchannelamplifiers
ConnectionDiagram
8-PinSOIC
InvertingFrequencyResponse
20038535
TopView
20038515
©2005NationalSemiconductorCorporationDS200385www.national.com
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LMH6628AbsoluteMaximumRatings(Note1)
IfMilitary/Aerospacespecifieddevicesarerequired,pleasecontacttheNationalSemiconductorSalesOffice/Distributorsforavailabilityandspecifications.ESDTolerance(Note4)HumanBodyModelMachineModelSupplyVoltageShortCircuitCurrentCommon-ModeInputVoltageDifferentialInputVoltage
2kV200V13.5(Note3)V+-V−V+-V−MaximumJunctionTemperatureStorageTemperatureRangeLeadTemperature(soldering10sec)
+150˚C
−65˚Cto+150˚C
+300˚C
OperatingRatings(Note1)
ThermalResistance(Note5)PackageSOIC
TemperatureRangeNominalSupplyVoltage
(θJC)65˚C/W
(θJA)145˚C/W−40˚Cto+85˚C
±2.5Vto±6V
ElectricalCharacteristics(Note2)
VCC=±5V,AV=+2V/V,RF=100Ω,RG=100Ω,RL=100Ω;unlessotherwisespecified.Boldfacelimitsapplyatthetemperatureextremes.SymbolGBSSBWSSBWGFLGFPGFRLPDTRTSOSSRHD2HD3VNINXTLKAGOLVIODVIOIBNDIBNIOSIOSDPSRRCMRRICCParameter
GainBandwidthProduct-3dBBandwidth,AV=+1-3dBBandwidth,AV=+2GainFlatnessPeakingRolloff
LinearPhaseDeviationRiseandFallTimeSettlingTimeOvershootSlewRate
2ndHarmonicDistortion3rdHarmonicDistortionEquivalentInputNoiseVoltageCurrentCrosstalkOpen-LoopGainInputOffsetVoltageAverageDriftInputBiasCurrentAverageDriftInputOffsetCurrentAverageDrift
PowerSupplyRejectionRatioCommon-ModeRejectionRatioSupplyCurrent
PerChannel,RL=∞
604657547.57.0
1MHzto100MHz1MHzto100MHzInputReferred,10MHz
5653
22−6263
nV/pA/dBdB
Conditions
VO<0.5VPPVO<0.5VPPVO<0.5VPPVO<0.5VPPDCto200MHzDCto20MHzDCto20MHz1VStep2VStepto0.1%1VStep4VStep1VPP,10MHz1VPP,10MHz
300
0.0.1.14121550−65−74
dBdBdegnsns%V/µsdBcdBc
180Min
Typ200300100
Max
UnitsMHzMHzMHz
FrequencyDomainResponse
TimeDomainResponse
DistortionAndNoiseResponse
Static,DCPerformance
±.5
5
±2±2.6±20±30±6
mVµV/˚CµAnA/˚CµAnA/˚CdBdB
±.7
1500.3570629
1212.5
mA
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LMH6628ElectricalCharacteristics(Note2)
SymbolRINCINROUTVOVOLCMIRIOInputVoltageRangeOutputCurrent
Parameter
InputResistanceInputCapacitanceOutputResistanceOutputVoltageRange
(Continued)
VCC=±5V,AV=+2V/V,RF=100Ω,RG=100Ω,RL=100Ω;unlessotherwisespecified.Boldfacelimitsapplyatthetemperatureextremes.
Conditions
Common-ModeDifferential-ModeCommon-ModeDifferential-ModeClosed-LoopRL=∞RL=100ΩCommon-Mode
Min
Typ5002001.51.5.1
Max
UnitskΩkΩpFpFΩVVVmA
MiscellaneousPerformance
±3.2±3.1±50
±3.8±3.5±3.7±85
Note1:AbsoluteMaximumRatingsindicatelimitsbeyondwhichdamagetothedevicemayoccur.OperatingRatingsindicateconditionsforwhichthedeviceisintendedtobefunctional,butspecificperformanceisnotguaranteed.Forguaranteedspecifications,seetheElectricalCharacteristicstables.
Note2:ElectricalTablevaluesapplyonlyforfactorytestingconditionsatthetemperatureindicated.Factorytestingconditionsresultinverylimitedself-heatingofthedevicesuchthatTJ=TA.NoguaranteeofparametricperformanceisindicatedintheelectricaltablesunderconditionsofinternalselfheatingwhereTJ>TA.SeeNote6forinformationontemperaturede-ratingofthisdevice.\"Min/Maxratingsarebasedonproductcharacterizationandsimulation.Individualparametersaretestedasnoted.
Note3:Outputisshortcircuitprotectedtoground,howevermaximumreliabilityisobtainedifoutputcurrentdoesnotexceed160mA.Note4:Humanbodymodel,1.5kΩinserieswith100pF.Machinemodel,0ΩInserieswith200pF.
Note5:ThemaximumpowerdissipationisafunctionofTJ(MAX),θJAandTA.ThemaximumallowablepowerdissipationatanyambienttemperatureisPD=(TJ(MAX)-TA)/θJA.AllnumbersapplyforpackagessoldereddirectlyontoaPCboard.
OrderingInformation
Package8-pinSOIC
PartNumberLMH6628MALMH6628MAX
PackageMarkingLMH6628MA
TransportMedia
Rails
2.5kUnitsTapeandReel
NSCDrawing
M08A
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LMH6628TypicalPerformanceCharacteristics
lessspecified)
Non-InvertingFrequencyResponse
(TA=+25˚,AV=+2,VCC=±5V,Rf=100Ω,RL=100Ω,un-InvertingFrequencyResponse
20038513
20038515
FrequencyResponsevs.LoadResistanceFrequencyResponsevs.OutputAmplitude
2003852520038510
FrequencyResponsevs.CapacitiveLoadGainFlatness&LinearPhase
20038516
20038524
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LMH6628TypicalPerformanceCharacteristics(TA=+25˚,AV=+2,VCC=±5V,Rf=100Ω,RL=100Ω,unless
specified)(Continued)
ChannelMatching
ChanneltoChannelCrosstalk
20038514
20038509
PulseResponse(VO=2V)PulseResponse(VO=100mV)
2003851120038512
2ndHarmonicDistortionvs.OutputVoltage3rdHarmonicDistortionvs.OutputVoltage
2003850720038508
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LMH6628TypicalPerformanceCharacteristics(TA=+25˚,AV=+2,VCC=±5V,Rf=100Ω,RL=100Ω,unless
specified)(Continued)
2nd&3rdHarmonicDistortionvs.Frequency
PSRRandCMRR(±5V)
2003851720038522
PSRRandCMRR(±2.5V)ClosedLoopOutputResistance(±2.5V)
2003852320038518
ClosedLoopOutputResistance(±5V)OpenLoopGain&Phase(±2.5V)
2003851920038521
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LMH6628TypicalPerformanceCharacteristics(TA=+25˚,AV=+2,VCC=±5V,Rf=100Ω,RL=100Ω,unless
specified)(Continued)
OpenLoopGain&Phase(±5V)
RecommendedRSvs.CL20038520
20038526
DCErrorsvs.Temperature
MaximumVOvs.RL20038546
20038545
2-Tone,3rdOrderIntermodulationInterceptVoltage&CurrentNoisevs.Frequency
20038544
20038547
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LMH6628TypicalPerformanceCharacteristics(TA=+25˚,AV=+2,VCC=±5V,Rf=100Ω,RL=100Ω,unless
specified)(Continued)
SettlingTimevs.Accuracy
20038548
ApplicationSection
LOWNOISEDESIGN
UltimatelownoiseperformancefromcircuitdesignsusingtheLMH6628requirestheproperselectionofexternalresis-tors.ByselectingappropriatelowvaluedresistorsforRFandRG,amplifiercircuitsusingtheLMH6628canachieveoutputnoisethatisapproximatelytheequivalentvoltageinput
multipliedbythedesiredgain(AV).noiseof2nV/
DCBIASCURRENTSANDOFFSETVOLTAGES
CancellationoftheoutputoffsetvoltageduetoinputbiascurrentsispossiblewiththeLMH6628.Thisisdonebymakingtheresistanceseenfromtheinvertingandnon-invertinginputsequal.Oncedone,theresidualoutputoffsetvoltagewillbetheinputoffsetvoltage(VOS)multipliedbythedesiredgain(AV).NationalApplicationNoteOA-7offersseveralsolutionstofurtherreducetheoutputoffset.OUTPUTANDSUPPLYCONSIDERATIONS
With±5Vsupplies,theLMH6628iscapableofatypicaloutputswingof±3.8Vunderano-loadcondition.Additionaloutputswingispossiblewithslightlyhighersupplyvoltages.Forloadsoflessthan50Ω,theoutputswingwillbelimitedbytheLMH6628’soutputcurrentcapability,typically85mA.Outputsettlingtimewhendrivingcapacitiveloadscanbeimprovedbytheuseofaseriesoutputresistor.Seetheplotlabeled\"RSvs.CL\"intheTypicalPerformancesection.LAYOUT
Properpowersupplybypassingiscriticaltoinsuregoodhighfrequencyperformanceandlownoise.De-couplingcapaci-torsof0.1µFshouldbeplacedascloseaspossibletothepowersupplypins.Theuseofsurfacemountedcapacitorsisrecommendedduetotheirlowseriesinductance.
Agoodhighfrequencylayoutwillkeeppowersupplyandgroundtracesawayfromtheinvertinginputandoutputpins.Parasiticcapacitancefromthesenodestogroundcausesfrequencyresponsepeakingandpossiblecircuitoscillation.
SeeOA-15formoreinformation.Nationalsuggeststhe730036(SOIC)dualopampevaluationboardasaguideforhighfrequencylayoutandasanaidindeviceevaluation.ANALOGDELAYCIRCUIT(ALL-PASSNETWORK)
ThecircuitinFigure1implementsanall-passnetworkusingtheLMH6628.Awidebandwidthbuffer(LM7121)drivesthecircuitandprovidesahighinputimpedanceforthesource.AsshowninFigure2,thecircuitprovidesa13.1nsdelay(withR=40.2Ω,C=47pF).RFandRGshouldbeofequalandlowvalueforparasiticinsensitiveoperation.
20038501
FIGURE1.
20038502
FIGURE2.DelayCircuitResponseto0.5VPulse
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LMH6628ApplicationSection
(Continued)
Thecircuitgainis+1andthedelayisdeterminedbythefollowingequations.
(1)
Td=
1dφ360df
;
(2)
whereTdisthedelayoftheopampatAV=+1.
TheLMH6628providesatypicaldelayof2.8nsatits−3dBpoint.
FULLDUPLEXDIGITALORANALOGTRANSMISSIONSimultaneoustransmissionandreceptionofanalogordigitalsignalsoverasinglecoaxialcableortwisted-pairlinecanreducecablingrequirements.TheLMH6628’swideband-widthandhighcommon-moderejectioninadifferentialam-plifierconfigurationallowsfullduplextransmissionofvideo,telephone,controlandaudiosignals.
InthecircuitshowninFigure3,oneoftheLMH6628’sampsisusedasa\"driver\"andtheotherasadifference\"receiver\"amplifier.Theoutputimpedanceofthe\"driver\"isessentiallyzero.ThetwoR’sarechosentomatchthecharacteristicimpedanceofthetransmissionline.The\"driver\"opampgaincanbeselectedforunityorgreater.
ReceiveramplifierA2(B2)isconnectedacrossRandformsdifferentialamplifierforthesignalstransmittedbydriverA2(B2).IfRFequalsRG,receiverA2(B1)willthenrejectthesignalsfromdriverA1(B1)andpassthesignalsfromdriverB1(A1).
FIGURE4.
20038531
POSITIVEPEAKDETECTOR
TheLMH6628’sdualamplifierscanbeusedtoimplementaunity-gainpeakdetectorcircuitasshowninFigure5.
20038505
FIGURE5.
TheacquisitionspeedofthiscircuitislimitedbythedynamicresistanceofthediodewhenchargingChold.Aplotofthecircuit’sperformanceisshowninFigure6witha1MHzsinusoidalinput.
20038503
FIGURE3.
Theoutputofthereceiveramplifierwillbe:
(3)
Caremustbegiventolayoutandcomponentplacementtomaintainahighfrequencycommon-moderejection.TheplotofFigure4showsthesimultaneousreceptionofsignalstransmittedat1MHzand10MHz.
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LMH6628ApplicationSection
(Continued)
(4)
Tobuildaboostcircuit,usethedesignequationsEq.6andEq.7.
(5)
20038537
FIGURE6.
Acurrentsource,builtaroundQ1,providesthenecessarybiascurrentforthesecondamplifierandpreventssaturationwhenpowerisapplied.Theresistor,R,closestheloopwhilediodeD2preventsnegativesaturationwhenVINislessthanVC.AMOS-typeswitch(notshown)canbeusedtoresetthecapacitor’svoltage.
Themaximumspeedofdetectionislimitedbythedelayoftheopampsandthediodes.TheuseofSchottkydiodeswillprovidefasterresponse.
ADJUSTABLEORBANDPASSEQUALIZER
A\"boost\"equalizercanbemadewiththeLMH6628bysummingabandpassresponsewiththeinputsignal,asshowninFigure7.
(6)
SelectR2andCusingEq.6.Usereasonablevaluesforhighfrequencycircuits-R2between10Ωand5kΩ,Cbetween10pFand2000pF.UseEq.7todeterminetheparallelcom-binationofRaandRb.SelectRaandRbbyeitherthe10Ωto5kΩcriteriaorbyotherrequirementsbasedontheimped-anceViniscapableofdriving.Finishthedesignbydetermin-ingthevalueofKfromEq.8.
(7)
Figure8showsanexampleoftheresponseofthecircuitofFigure9,wherefois2.3MHz.Thecomponentvaluesareasfollows:Ra=2.1kΩ,Rb=68.5Ω,R2=4.22kΩ,R=500Ω,KR=50Ω,C=120pF.
20038506
20038543
FIGURE7.
TheoveralltransferfunctionisshowninEq.5.
FIGURE8.
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LMH6628DualWideband,LowNoise,VoltageFeedbackOpAmpPhysicalDimensions
unlessotherwisenoted
inches(millimeters)
8-PinSOIC
NSPackageNumberM08A
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