ScienTECH AB65 User manual

AB65
PhaseShiftOscillator
OperatingManual
Ver.1.1
AnISO9001:2000company
94-101,ElectronicComplexPardesipura,
Indore-452010,India
Tel:[phone]
Fax:[phone]
email : [e-mail]
Website: www.scientech.bz
Toll free :1800-103-5050

AB65
ScientechTechnologies Pvt.Ltd.2

AB65
ScientechTechnologies Pvt.Ltd.3
RoHSCompliance
ScientechProductsareRoHSComplied.
RoHSDire
ctiveconcernswiththerestrictiveuseofHazardoussubstances(Pb,
Cd,Cr, Hg,Brcompounds)inelectricandelectronicequipments.
Scientechproductsare“LeadFree” and“EnvironmentFriendly”.
Itismandatorythatserviceengineersuseleadfreesold
erwireandusethe
solderingironsupto(25W)thatreachatemperatureof450°Catthetipasthe
meltingtemperatureoftheunleadedsolderishigherthantheleadedsolder.
AB65
PhaseShiftOscillator
TableofContents
1. Introduction4
2. Theory6
3. Experiments9
StudyofPhaseShiftoscillatorwithandwithoutBuffer
betweenRC Section
4. DataSheet12
5. Warranty14
6. ListofAccessories14

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Introduction
AB65 isacompact,readytouse PhaseShift Oscillator experimentboard.Thisis
usefulforstudentstounderstandfunctionalityofphaseshiftoscillator.Studentcan
alsosee phaseshiftintroducedbydifferentRC stagesofaphaseshiftoscillator.Itcan
beusedasstandaloneunitwithexternalDCPowerSupplyorcanbeusedwith
ScientechAnalog LabST2612 whichhasbuiltinDCPowerSupply,ACPower
Supply,functiongenerator,modulationgenerator,continuitytester,toggleswitches,
andpotentiometer.
ListofBoards:
ModelName
AB01 Diodecharacteristics(Si, Zener,LED)
AB02 Transistorcharacteristics(CBNPN)
AB03 Transistorcharacteristics(CBPNP)
AB04 Transistorcharacteristics(CE NPN)
AB05 Transistorcharacteristics(CEPNP)
AB06 Transistorcharacteristics(CCNPN)
AB07 Transistorcharacteristics(CCPNP)
AB08 FETcharacteristics
AB09 RectifierCircuits
AB10 Wheatstonebridge
AB11 Maxwell’sBridge
AB12 DeSauty’sBridge
AB13 Schering Bridge
AB14 DarlingtonPair
AB15 CommonEmitterAmplifier
AB16 CommonCollectorAmplifier
AB17 CommonBaseAmplifier
AB18 RC-CoupledAmplifier
AB19 CascodeAmplifier
AB20 DirectCoupledAmplifier
AB21 Class AAmplifier
AB22 Class BAmplifier(pushpullemitterfollower)
AB23 Class CTunedAmplifier
AB24 TransformerCoupledAmplifier
AB25 PhaseLockedLoop (FMDemodulator&Frequency
Divider/Multiplier)
AB26 FETAmplifier
AB27 VoltageControlledOscillator
AB28 Multivibrator(Mono stable/Astable)
AB29 F-VandV-FConverter
AB30 V-IandI-VConverter
AB31 ZenerVoltageRegulator
AB32 TransistorSeriesVoltageRegulator

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AB33 TransistorShuntVoltageRegulator
AB35 DCAmmeter
AB37 DCAmmeter(0-2mA)
AB39 InstrumentationAmplifier
AB41 DifferentialAmplifier(Transistorized)
AB42 OperationalAmplifier(Inverting /Non-inverting/Differentiator)
AB43 OperationalAmplifier(Adder/Scalar)
AB44 OperationalAmplifier(Integrator/Differentiator)
AB45 Schmitt TriggerandComparator
AB49 KDerivedFilter
AB51 Activefilters(LowPass andHighPass)
AB52 ActiveBandPass Filter
AB54 Tschebyscheff Filter
AB56 FiberOpticAnalogLink
AB57 Owen’sBridge
AB58 Anderson’sBridge
AB59 Maxwell’sInductance Bridge
AB64 RC –CoupledAmplifierwithFeedback
AB66 WienBridgeOscillators
AB67 Colpitt Oscillator
AB68 HartleyOscillator
AB80 RLCSeriesandRLCParallelResonance
AB82 Thevenin’sandMaximumPowerTransferTheorem
AB83 ReciprocityandSuperpositionTheorem
AB84 Tellegen’sTheorem
AB85 Norton’stheorem
AB88 DiodeClipper
AB89 DiodeClampers
AB90 Twoportnetworkparameter
AB91 OpticalTransducer(Photovoltaiccell)
AB92 OpticalTransducer(Photoconductivecell/LDR)
AB93 OpticalTransducer(Phototransistor)
AB96 TemperatureTransducer(RTD&IC335)
AB97 TemperatureTransducer(Thermocouple)
AB101 DSBModulatorandDemodulator
AB102 SSBModulatorandDemodulator
AB106 FMModulatorandDemodulator
andmanymore…………

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Theory
Oscillatorsarecircuitsthatproduce periodicwaveformswithoutinputotherthan
perhapsatrigger.Theygenerallyusesomeformofactivedevice,lamp,orcrystal,
surroundedbypassivedevicessuchasresistors,capacitors,andinductors,togenerate
theoutput.
Therearetwomainclassesofoscillator:RelaxationandSinusoidal.Relaxation
oscillatorsgeneratethetriangular,sawtoothand othernon-sinusoidalwaveforms.
Sinusoidaloscillatorsconsistofamplifierswithexternalcomponentsusedtogenerate
oscillation,orcrystalsthatinternallygeneratetheoscillation.Thefocushereison
sinewaveoscillators,createdusingoperationalamplifiers“Op-Amps”.Sinewave
oscillatorsareusedasreferencesortestwaveformsbymanycircuits.
Anoscillatorisatypeoffeedbackamplifierinwhichpartoftheoutputisfedbackto
theinputviaafeedbackcircuit.If thesignalfedbackisofpropermagnitudeand
phase,thecircuitproducesalternating currentsorvoltages.Tworequirementsfor
oscillationare:
1. Themagnitudeoftheloop gainAVBmustbeatleast1.
2. Thetotalphaseshiftoftheloop gainAV Bmustbeequalto0°or360°.Ifthe
amplifiercausesaphaseshiftof180°,thefeedbackcircuitmustprovidean
additionalphaseshiftof180°sothatthetotalphaseshiftaroundtheloop is
360°.
Figure1showsaphaseshiftoscillator, whichconsistsofanop-ampastheamplifying
stageandthreeRC cascadednetworksasthefeedbackvoltagefromtheoutputbackto
theinputoftheamplifier.Theop-ampisusedintheinvertingmode;therefore,any
signalthatappearsattheinvertingterminalisshiftedby180°attheoutput.An
additional180°phaseshiftrequiredforoscillationisprovidedbythecascadedRC
networks.Thusthetotalphaseshiftaroundtheloopis360°(or0°).Atsomespecific
frequencywhenthephaseshiftofthecascadedRCnetworksisexactly180°andthe
gainoftheamplifierissufficientlylarge,thecircuitwilloscillateatthatfrequency.
Thisfrequencyiscalledthefrequencyofoscillation, f0,andit isgivenby
f0 =1.732/2 πRC

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ScientechTechnologies Pvt.Ltd.7
Figure1
Aphase-shiftoscillatorcanbebuiltwithoneOp-Amp isshownabovethenormal
assumptionisthatthephaseshiftsectionsareindependentofeachother.Then
Equationiswritten
AB=A[l/RCs +1]3
Theloop phaseis-180°whenthephaseshiftofeachsectionis-60°,andthisoccurs
when ω=1.732/2πRC becausethetangentof60°=1.732.Theoscillationfrequency
withthecomponentvaluesshowninfigure1isslightlydifferentthanthecalculated
oscillation frequency.Thesediscrepanciesarepartiallyduetothecomponent
variations,butthebiggestcontributing factoristheincorrectassumptionthattheRC
sectiondoesnotloadeachother.Thiscircuit configurationwasverypopularwhen
activecomponentswerelargeandexpensive,butnowOp-Ampsareinexpensiveand
small andcomefourinapackage, sothesingleop-ampphase-shiftoscillatorislosing
popularity.

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BufferedPhase-ShiftOscillator:
Thebufferedphaseshiftoscillatorshowninfigure2oscillatesveryclosetothe
calculatedfrequency.
Figure2
ThebufferpreventtheRC sectionsfrom loadingeachother,hencethebufferedphase
shiftoscillatorperformsclosertothecalculatedfrequencyandgain.Thegainsetting
resistor,R1,loadsthethirdRC section,andifthefourthop-ampinaquadop amp
buffersthisRC section,theperformancebecomesidle. Low-distortionsinewavescan
beobtainedfrom eitherphase-shiftoscillator,butthepurestsinewaveistakenfrom
theoutputofthelastRC section.
Thisisahigh-impedancenode,soahigh-impedanceinputismandatedtoprevent
loadingandfrequencyshiftingwithloadvariations.

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ScientechTechnologies Pvt.Ltd.9
Experiment
Objective:
StudyofPhaseShiftOscillatorwithand withoutbufferbetweenRC sections
EquipmentsNeeded:
1. Analogboard, AB65.
2. DCpowersupplies-12V,+12Vfromexternalsourceor ST2612AnalogLab.
3. 2mmpatchcords.
Circuitdiagram:
Circuit usedtoplotdifferentcharacteristicsoftransistorisasshowninfigure3
Figure3

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Procedure :
•TostudyphaseshiftoscillatorwithoutbufferbetweenRC sectionsproceedas
follows:
1. Connect+12V,-12VDCpowersuppliesattheirindicatedpositionfrom
externalsource or ST2612Analog Lab.
2. Connecta2mm patchcordbetweentestpointB&C, D&E, F&A
3. Switch‘On’thePowerSupply.
4. MeasurefrequencyatanytestpointsT1,T2, T3, T4usingCRO.
5. Comparemeasuredfrequencywiththetheoreticallycalculatedvalue.
6. MeasurephasedifferencebetweentestpointsTl&T2,T2&T3,T3&T4,and
T4&T1withthehelpofdualchannelCRO.
7. VarygainPotentiometerof470Ktoadjustgainoftheamplifierincaseof
clippedwaveform.
Results:
1. Theoreticalvalueofoutputfrequency=____________
2. Practicalvalueofoutputfrequency=____________
3. PhaseshiftbetweenTestPointT1&T2=____________
4. PhaseshiftbetweenTestPointT2&T3=____________
5. PhaseshiftbetweenTestPointT3&T4=____________
6. PhaseshiftbetweenTestPointT4&T1=____________
•TostudyphaseshiftoscillatorwithbufferbetweenRCsectionsproceedas
follows:
1. Connect+12V,-12VDCpowersuppliesattheirindicatedpositionfrom
externalsource or ST2612Analog Lab.
2. Connecta2mmpatchcordbetweenTestPointB&G,C&H,D&I,E&J, F
&K, L &A.
3. Switch‘On’thePowerSupply.
4. MeasurefrequencyatanytestpointsT1,T2, T3, T4usingCRO.
5. Comparemeasuredfrequencywiththetheoreticallycalculatedvalue.
7. MeasurephasedifferencebetweentestpointsT1&T2,T2&T3,
T3&T4,T4andT1withthehelpofdualchannelCRO.
8. VarygainPotentiometerof470Ktoadjustgainoftheamplifierincaseof
clippedwaveform.