SRS Labs SR555 User manual

Model SR555 / SR556
Operation Manual
Current Preamplifier
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Stanford Research Systems
1290-D Reamwood Ave
Sunnyvale, CA 94089 U.S.A.
Phone: [phone] FAX: [phone]
[email protected] •www.thinkSRS.com
Copyright © 2012
Stanford Research Systems, Inc.
All Rights Reserved
Revision 1.2 (Nov 2012)

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Certification
StanfordResearchSystemscertifiesthatthisproductmetitspublishedspecificationsatthetimeof
shipment.
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Warranty
TheStanfordResearchSystemsproductiswarrantedagainstdefectsinmaterialsandworkmanshipfora
periodofone(1)yearfromthedateofshipment.
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Service
Forwarrantyserviceorrepair,thisproductmustbereturnedtoaStanfordResearchSystemsauthorized
servicefacility.ContactStanfordResearchSystemsoranauthorizedrepresentativebeforereturning
thisproductforrepair.
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Informationinthisdocumentissubjecttochangewithoutnotice.
ThismanualisSRSPartNumber9‐01686‐903.

3of10
1. Specifications
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SR555SR556
Gain(Transimpedance)
Gainaccuracy
Gainstability
107V/A
±1%
±50ppm/°C
109V/A
±1%
±50ppm/°C
Bandwidth
Rise‐/Fall‐time
DC–120kHz(‐3dB)
2.9µs
DC–3kHz(‐3dB)
120µs
Inputcurrentnoise(typ)42fA/√Hz@1kHz5.0fA/√Hz@1kHz
Inputvoltagenoise(typ)4.5nV/√Hz@1kHz
Inputbiascurrent 3pAtyp.
Inputoffsetvoltage±150µVmax
Inputvoltagerange‐9V–+9V(Outsideofthisrangemaycausepermanentdamage)
Inputresistance(DC)
Inputcapacitance
50
16pF
50
12pF
Inputcurrentrange±1µA(forlinearoperation)±10nA(forlinearoperation)
ExternalinputcapacitanceUpto1nFUpto10nF
Biasinput
Biasinputimpedance
‐5–+5Vdc
1M
Biasrejection ‐76dBtyp.(OutputresponsetoDCbiasinput)
Biassettlingtime<150ms<250ms
Output
20Vppmax,balanceddifferential
10mAmax
50Ωoutputimpedance
Power
+20V±10%/80mA
‐20V±10%/50mA
(SuppliedbySR510,SR530,SR810,SR830,orSR124viacontrolcable)
Mechanical3.1”×1.4”×5.1”(WHD)
Weight10oz
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2. TypicalCharacteristics
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1.E+05
1.E+06
1.E+07
1.E+08
1.E+09
1.E+10
10 100 1000 10000 100000 1000000
Gain(V/A)
Frequency(Hz)
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
10 100 1000 10000 100000
Inputimpedance()
Frequency(Hz)
SR556
SR555
Fi
g
ure1:Gain
Fi
g
ure2:In
p
utim
p
edance
Cs=1.2nF
Cs=12nF
SR556
SR555
Csistheinput shuntcapacitance

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1
10
100
1000
10000
10 100 1000 10000 100000 1000000
Currentnoisedensity(fA/Hz)
Frequency(Hz)
1
10
100
1000
10000
10 100 1000 10000 100000 1000000
Currentnoisedensity(fA/Hz)
Frequency(Hz)
Cs=1.2nF
Csistheinput shuntcapacitance
Csistheinput shuntcapacitance
Cs=120pF
Cs=12nF
Cs=1.2nF
Figure3:SR555input
currentnoisedensity
Figure4:SR556input
currentnoisedensity

6of10
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1
10
100
1
Voltagenoisedensityen(nV/Hz)
10
Fron
Figure6:SR5
1
0
t
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
55/SR556M
e
0
01
0
Frequency(
H
5.1”
e
chanical
0
00 1
0
H
z)
Rea
r
Figure
5
inputv
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0
000
1
3.1”
r
5
:SR555/SR
5
oltagenoise
d
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1
00000
1.4”
5
56
d
ensity

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3. Description
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TheblockdiagrambelowshowstheSR555/SR556currentamplifierwhichconvertsinputcurrentintoa
differentialoutputvoltage.Thetotaldifferentialoutputvoltageisgivenby
  .Acurrent
amplifierisalsocalledaTransimpedanceAmplifier,oraTIA.
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Figure7AblockdiagramofSR555/SR556currentamplifiers
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Unlikeasimpleresistor,thetransimpedanceamplifierpresentsalow‐impedancenodetothesource.
Thisnodeisgenerallyavirtualground.IntheSR555/SR556,thisnodevoltagecanbesetattheuser
providedvoltagebyswitchingto“BiasEnable”.Thisbiasvoltagewillnotbepresentintheoutputsignal
sinceitissubtractedoutbythepostdifferentialamplifier.
TheSR555/SR556canbelocatedclosetothesourcetoeliminatelongcables,capacitiveloadingand
noisepickup.Thetwooutputsignalsshouldbeuseddifferentiallyforbestresults.Thecapacitancefrom
longinputcablesorintrinsiccapacitancefromtheinputsourcewilladduptothetotalsource
capacitance.Thiswillreactwiththeopampvoltagenoiseen(showninFigure5)toaddaneffective
currentnoiseof2totheequivalentinputnoise,asshowninFigures3and4(so‐called“noise
gainpeaking”).Itshouldbenotedthathasvirtuallynoeffectonthesignalgain,asshowninFigure1.
TheSR555andSR556areideallow‐noisecurrentpreamplifiersforSRS’lock‐inamplifiers,andcanalso
beusedforanyothersmallcurrentdetectionpurposes.
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4. UsingtheSR555/SR556withaLockIn
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PowerissuppliedtotheSR555/SR556viathe9pincablewhichissuppliedwiththeunit.Ifitisusedasa
pre‐amplifierforaSRS’lock‐inamplifier,attachoneendofthecabletotheconnectorontherearofthe
SR555/SR556.Withthelock‐inpoweroff,connecttheotherendofthecabletothe“PREAMP”
connectorontherearofthelock‐in.Bothendsofthecableareequivalent.Ifalongercableisrequired,
anystandardcablewithmale9‐pinD‐subconnectorsonbothsides,wiredpin‐to‐pin,willsuffice.
TheOutputAoftheSR555/SR556shouldbeconnectedtothe(A)Inputofthelock‐in.TheOutputB
shouldbeconnectedtothe(B)Inputofthelock‐in.Equal‐length,BNC‐terminatedcoaxcablesshouldbe
usedforbothconnections,andforbestresultsthetwocablesmaybetwistedtogethertominimize
inductivepickup.Thelock‐inInputSelectorshouldbesetto(A–B).Notethattheoutputofthe
SR555/SR556isabalanced,differentialsignalpresentedacrosstheAandBoutputs,makingitimportant
toreceivetheoutputsignaldifferentially.
Forapplicationsinwhichtheinputcurrentnodeshouldbeleftunbiased(0Vpotential),the“Bias
Enable”switchshouldbeleftinthedownpositionontheSR555/SR556.
Forapplicationsinwhichanon‐zeropotentialistobeestablishedattheinputcurrentnode,the“BIAS
IN”BNCconnectorisused.ThisisaDCinputthatprogramsthenon‐invertingnodeoftheinputopamp,
andsetsthevoltageofinputcurrentsignal.TheDCbiasvoltageissubtractedbythedifferential
amplifierandwillnotbesensedbythelock‐inamplifier.
Theoverallsensitivityofthelock‐inplusthepreamplifierisnotdisplayedonthelock‐infrontpanel.Itis
necessarytodividethedisplayedsensitivitybythepreamplifiergain:10V/AfortheSR555,or10V/A
fortheSR556.
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5. UsingtheSR555/SR556withoutaLockIn
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TheSR555/SR556canbepoweredwithanexternalpowersupply.Powerisappliedthroughthe9pin
connectorasdescribedinthetablebelow:
PinVoltageCurrent
1+20VDC±10%80mA
6–20VDC±10%50mA
7,8Ground
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BothDCvoltagesarerequired.EitherPin7orpin8,orbothmaybeusedasground.Allotherpinsare
notused.Therearetwoprotectiondiodesconnectedbetweentheinternalregulatorsandthe+20Vand
‐20Vinputpins.
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6. CircuitDescription
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ThetransimpedenceamplifierconsistsofopampsU1,U2andgainresistorR7(R3forSR555).Input
currentcomingthroughJ1andR1willpassthroughR7andsinktotheoutputnodeofU2.A
correspondingvoltagewillbepresentatTP1.ThebiasvoltagesignalfromJ2islow‐passfilteredandfed
tothenon‐invertingnodeofU1.R8throughR10,C3,andC25formthelowpassfilter,andarebuffered
byafollowerU3.SW1isusedtoenableordisablethebiasvoltage.TP2iseithergroundedorequalto
thefollowerU3outputvoltage.U4andRN1formafullydifferentialamplifier/lowpassfilterwhose
differentialoutputisproportionaltothecurrentsignalfromJ1(biasvoltageissubtracted).
U5andU6regulatetheDCpowerinputsfromconnectorJ5toprovideinternal±15Vpowersupplies.
U11providethe+5VandusedbyU10andoverloadLED.
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7. PartsLists
a. SR555
Part
NumberReferenceValue
5‐00570C3,C25.1U
5‐00299
C4,C5,C8,C9,C10,
C11,C17,C18,C24.1U
5‐00260C6,C7470U
5‐00383C12470P
5‐00377C13,C14150P
5‐00848
C19,C20,
C21,C22,C231.0U
3‐00230D1,D51N5240A
3‐00945D2BAT54S
3‐00010D3GREEN
3‐00011D4RED
3‐00003D6,D71N4001
1‐01344J5DB‐9Female
1‐01320J6,J75PIN
6‐00174L1,L26611TYPE43
4‐00191R1,R12,R1349.9
4‐01760RN1668‐A‐2001‐A
4‐00925R2,R6,R2310
4‐02539R310.0M
4‐01021R4100
4‐01213R510.0K
4‐01551R81.0M
4‐01309R9,R10,R24100K
4‐00800R111
4‐01184
R15,R17,R18,
R19,R20,R304.99K
4‐01181R16,R214.64K
4‐01347R22249K
4‐01088R25,R26,R27,R28499
2‐00022SW1DPDT
3‐00998U3OPA227
3‐02155U4THS4131
3‐00711U578L15
3‐01301U679L15
3‐00728U7,U8,U9LM393
3‐00662U1074HC14
3‐00116U11LM78L05
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b. SR556
Part
NumberReferenceValue
5‐00389C21500P
5‐00570C3,C25.1U
5‐00299
C4,C5,C8,C9,C10,
C11,C17,C18,C24.1U
5‐00260C6,C7470U
5‐00456C12.015U
5‐00450C13,C14.0047U
5‐00848
C19,C20,
C21,C22,C231.0U
3‐00230D1,D51N5240A
3‐00945D2BAT54S
3‐00010D3GREEN
3‐00011D4RED
3‐00003D6,D71N4001
1‐01344J5DB‐9Female
1‐01320J6,J75PIN
6‐00174L1,L26611TYPE43
4‐00191R1,R12,R1349.9
4‐01760RN1668‐A‐2001‐A
4‐00925R2,R2310
4‐01021R4100
4‐01213R510.0K
4‐01261R631.6K
4‐02537R71.00G
4‐01551R81.0M
4‐01309R9,R10,R24100K
4‐00800R111
4‐01184
R15,R17,R18,
R19,R20,R304.99K
4‐01181R16,R214.64K
4‐01347R22249K
4‐01088R25,R26,R27,R28499
2‐00022SW1DPDT
3‐00998U3OPA227
3‐02155U4THS4131
3‐00711U578L15
3‐01301U679L15
3‐00728U7,U8,U9LM393
3‐00662U1074HC14
3‐00116U11LM78L05
