Table Of ContentANALOGCIRCUITSANDSIGNALPROCESSING
SeriesEditors:
MohammedIsmail.TheOhioStateUniversity
MohamadSawan.E´colePolytechniquedeMontre´al
For furthervolumes:
http://www.springer.com/series/7381
Raj Senani (cid:129) D.R. Bhaskar (cid:129) A.K. Singh
V.K. Singh
Current Feedback
Operational Amplifiers
and Their Applications
RajSenani D.R.Bhaskar
DivisionofElectronics JamiaMilliaIslamia
andCommunicationEngineering ElectronicsandCommunication
NetajiSubhasInstitute Engineering
ofTechnology F/OEngineeringandTechnology
NewDelhi,India NewDelhi,India
A.K.Singh V.K.Singh
ElectronicsandCommunication DepartmentofElectronicsEngineering
Engineering InstituteofEngineeringandTechnology
HRCTGroupofInstitutions Lucknow,India
F/OEngineeringandTechnology
Mota,Ghaziabad,India
ISBN978-1-4614-5187-7 ISBN978-1-4614-5188-4(eBook)
DOI10.1007/978-1-4614-5188-4
SpringerNewYorkHeidelbergDordrechtLondon
LibraryofCongressControlNumber:2012955675
#SpringerScience+BusinessMediaNewYork2013
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Preface
In spite of all electronic systems prominently being dominated by digital circuits
and systems, the analog circuits have neither become obsolete nor avoidable.
In fact, despite the dominance of digital circuits, analog circuits and techniques
continue to be indispensable and unavoidable in many areas since all real life
signals are analog in nature. Thus, several types of processing of natural signals
or interface of such signals with digital processing circuits has to be necessarily
carried out by analog circuits. Also, many basic functions such as amplification,
rectification,continuous-timefiltering,analog-to-digitalconversionanddigital-to-
analogconversionetc.needanalogcircuitsandtechniques.
Traditionally,theintegratedcircuit(IC)op-amphasusuallybeenconsideredto
be the workhorse of all analog circuit designs. However, over the years, it was
foundthattherearemanysituationssuchasrealizationofvoltagecontrolledcurrent
sources, current controlled current sources, instrumentation amplifiers, non-
inverting integrators and non-inverting differentiators etc., where the traditional
voltage mode op-amp (VOA)-based circuits suffer from two drawbacks namely
employment of more than the minimum required number of passive components
andrequirementofperfectmatchingofseveralofthem(duetowhichanymismatch
maynotonlydeterioratetheperformanceoftheintendedcircuitsbutmayalsolead
to instability in some cases). Furthermore, VOA-based amplifiers exhibit a gain
bandwidthconflictandtheirfrequencyrangeofoperationislimitedbytheeffectof
finite gain bandwidth product (GBP) of the op-amps on one hand and due to the
slew-induced distortion (resulting due to finite slew rate of the op-amps) on the
otherhand.Consequently,therehasbeencontinuoussearchforalternativeanalog
circuit building blocks to overcome these difficulties while still matching the
versatilityoftheVOAsinrealizingalmostallkindsofanalogfunctions.
During the past four decades, many alternative new analog circuit building
blocks have been proposed out of which only the Operational Transconductance
Amplifiers, Current Conveyors and Current Feedback Operational Amplifiers
have been made available as of-the-shelf ICs and have therefore attracted the
attention of educators, researchers and circuit designers worldwide who have
explored their various applications. Among these building blocks, the current
v
vi Preface
feedback operational amplifier (CFOA), sometimes also referred as operational
trans-impedance amplifier, has received notable attention in literature because of
its two very significant properties namely, a very high slew rate (theoretically
infinite;practicallyashighasseveralthousandvoltsperμsasagainstaverymodest
0.5 V/μs for the general purpose and most popular μA741 type op-amp) and its
capabilityofofferinggainbandwidthdecoupling(therebyimplyingthefeasibility
of maintaining essentially a constant bandwidth and variable gain, for low to
medium values of the gains). Though CFOAs have some limitations as compared
tothetraditionalVOAs,theiradvantageousfeaturescoupledbytheirversatilityand
flexibility,particularlyofaspecifictypewhichhasitscompensationpinaccessible
externally,overshadowstheirdemeritsinanumberofapplications.
ThismonographisbasicallyconcernedwithCFOAsandtheirapplicationsand
includes an extensive discussion about various typesof CFOAs, the basic circuits
realizable using them, their merits and demerits and their applications in the
realization of continuous time analog filters, simulation of inductors and other
type of impedances, synthesis of sinusoidal oscillators and miscellaneous linear
andnon-linearapplications(includingavarietyofrelaxationoscillatorsandchaotic
circuits).AlsocoveredarenumerousexamplesoftheuseofCFOAsinrealizinga
number of other newly proposed active circuit building blocks. The monograph
closesbygivingabriefaccountoftherecentdevelopmentsinthedesignofbipolar
andCMOSCFOAs,adiscussionaboutvariousmodifiedformsofCFOAsproposed
intherecentliteraturefromtimetotime,outliningthecurrentdirectionsofresearch
inthisareaandincludingasupplementarylistofreferencesforfurtherreading.
It is hoped that this monograph, which contains a comprehensive collection of
over 200 CFOA-based analog circuits with their relevant theory and design/
performance details, should turn out to be a useful source of reference for
academicians (both educators and students), practicing engineers and anybody
interestedinanalogcircuitdesign using CFOAs. Readers may also finda number
ofinterestingandchallengingproblemsworthyoffurtherinvestigations,fromthe
varioussuggestionsgivenintherespectivechaptersofthismonograph.
Contents
1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Prologue. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 AnOverviewofAnalogCircuitsandTheirApplications. . . . . . . 2
1.3 TheUbiquitousOp-Amp:TheDrawbacks
andLimitationsofSomeOp-AmpCircuits. . . . . . . . . . . . . . . . . 3
1.3.1 Op-AmpCircuitsWhichEmployMoreThan
theMinimumNumberofResistorsandRequire
PassiveComponent-Matching. . . . . . . . . . . . . . . . . . . . . 3
1.3.2 TheGain-BandwidthConflict. . . . . .. . . . . . . .. . . . . . .. 7
1.3.3 Slew-RateBasedLimitations. . . . . . . . . . . . . . . . . . . . . . 8
1.4 ABriefReviewoftheEvolutionofAlternativeAnalog
CircuitBuildingBlocks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.4.1 TheOperationalTransconductanceAmplifiers. . . . . . . . . 9
1.4.2 TheCurrentConveyors. . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.4.3 TheCurrentFeedbackOp-Amp(CFOA). . . . . . . . . . . . . 14
1.4.4 TheOperationalTrans-resistanceAmplifier. . . . . . . . . . . 15
1.4.5 TheFour-Terminal-Floating-Nullor. . . . . . . . . . . . . . . . . 17
1.4.6 TheCurrentDifferencingBufferedAmplifier. . . . . . . . . . 18
1.4.7 TheCurrentDifferencingTransconductance
Amplifier(CDTA). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
1.5 TheNecessityandtheScopeofthePresentMonograph. . . . . . . . 20
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2 CFOAs:Merits,Demerits,BasicCircuits
andAvailableVarieties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.2 AD844:TheCFOAwithExternally-Accessible
CompensationPin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.3 TheMeritsandtheAdvantageousFeaturesoftheCFOAs. . . . . . 28
2.3.1 TheReasonandtheOriginoftheHighSlewRate. . . . . . . 28
vii
viii Contents
2.3.2 De-couplingofGainandBandwidth:Realisability
ofVariable-Gain,Constant-BandwidthAmplifiers. . . . . . . 30
2.4 TheDemeritsandLimitationsofCFOAs. . . . . . . . . . . . . . . . . . . 31
2.4.1 Demerits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
2.4.2 DifficultieswithCapacitiveFeedback. . . . . . . . . . . . . . . . 32
2.4.3 EffectofStrayCapacitancesandLayoutIssues. . . . . . . . . 32
2.5 BasicCircuitsUsingCFOAs. . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
2.5.1 VCVSConfigurations. . . . . . . . . . . . . . . . . . . . . . . . . . . 32
2.5.2 InstrumentationAmplifierUsingCFOAs. . . . . . . . . . . . . 34
2.5.3 VCCS,CCVSandCCCSConfigurations. . . . . . . . . . . . . 35
2.5.4 UnityGainVoltageandCurrentFollowers. . . . . . . . . . . . 36
2.5.5 IntegratorsandDifferentiators. . . . . . . . . . . . . . . . . . . . . 36
2.6 CommerciallyAvailableVarietiesofCFOAs. . . . . . . . . . . . . . . . 42
2.6.1 TheMixed-Translinear-Cells(MTC)asBuilding
BlocksofCFOAs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
2.6.2 ElantecDual/QuadEL2260/EL2460. . . . . . . . . . . . . . . . . 44
2.6.3 IntersilHFA1130. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
2.6.4 AD8011fromAnalogDevices. . . . . . . . . . . . . . . . . . . . . 45
2.6.5 THS3001fromTexasInstrumentsInc.. .. . . .. . . .. . . .. 46
2.7 ConcludingRemarks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
3 SimulationofInductorsandOtherTypes
ofImpedancesUsingCFOAs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
3.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
3.2 AnOverviewofOp-Amp-RCCircuitsforGrounded
andFloatingInductorSimulationandTheirLimitations. . . . . . . . 49
3.3 RealizationofGyratorandGroundedImpedances
UsingCFOAs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
3.4 Single-CFOA-BasedGroundedImpedanceSimulators. . . . . . . . . 56
3.4.1 LossyGroundedInductors/FDNRs. . . . . . . . . . . . . . . . . . 57
3.4.2 Single-CFOA-BasedGroundedNegative
CapacitanceandNegativeInductanceSimulators. . . . . . . 60
3.5 FloatingInductorsandFloatingGeneralized
impedanceSimulatorsUsingCFOAs. . . . . . . . . . . . . . . . . . . . . . 60
3.6 FloatingInductanceCircuitsEmployingOnlyTwoCFOAs. . . . . 65
3.6.1 Lossless/LossyFloatingInductanceSimulator. . . . . . . . . . 65
3.6.2 ALossyFloatingInductanceSimulator. . . . . . . . . . . . . . 67
3.7 ApplicationsofSimulatedImpedances
inActiveFilterDesigns. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
3.7.1 ApplicationsintheDesignofSecondOrderFilters. . . . . . 68
3.7.2 ApplicationintheDesignofHigherOrderFilters. . . . . . . 69
3.8 RealizationofVoltage-ControlledImpedances. . . . . . . . . . . . . . . 71
3.8.1 GroundedVoltageControlledImpedanceSimulators. . . . . 72
3.8.2 FloatingVoltageControlledImpedanceSimulators. . . . . . 73
3.9 ConcludingRemarks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
Contents ix
4 DesignofFiltersUsingCFOAs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
4.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
4.2 TheFiveGenericFilterTypes,TheirFrequency
ResponsesandParameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
4.3 Voltage-Mode/Current-ModeBiquadsUsingCFOAs. . . . . . . . . . 83
4.3.1 DualFunctionVMBiquads. . . . . . . . . . . . . . . . . . . . . . . 83
4.3.2 SingleInputMultipleOutput(SIMO)
TypeVMBiquads. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
4.3.3 MultipleInputSingleOutput(MISO)
TypeVMBiquads. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
4.3.4 MISO-TypeUniversalCurrent-Mode(CM)Biquads. . . . . 99
4.3.5 Dual-ModeUniversalBiquadsUsing
SingleCFOA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
4.3.6 Mixed-ModeUniversalBiquads. . . . . . . . . . . . . . . . . . . . 103
4.4 Active-RMultifunctionVMBiquads. . . . . . . . . . . . . . . . . . . . . . 107
4.5 InverseActiveFiltersUsingCFOAs. . . . . . . . . . . . . . . . . . . . . . 110
4.6 MOSFET-CFiltersEmployingCFOAs. . . . . . . . . . . . . . . . . . . . 112
4.6.1 MOSFET-CFullyDifferentialIntegrators. . . . . . . . . . . . . 113
4.6.2 MOSFET-CFullyDifferentialBiquads. . . . . . . . . . . . . . . 115
4.6.3 MOSFET-CSingle-EndedBiquad. . . . . . . . . . . . . . . . . . 116
4.7 DesignofHigherOrderFiltersUsingCFOAs. . . . . . . . . . . . . . . 118
4.7.1 SignalFlowGraphBasedSynthesisofnth
OrderTransferFunctionUsingCFOAs. . . . . . . . . . . . . . . 119
4.7.2 DoublyTerminatedWaveActiveFilters
EmployingCFOA-BasedonLCLadder
Prototypes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
4.7.3 HigherOrderModularFilterStructures
UsingCFOAs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
4.8 ConcludingRemarks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
5 SynthesisofSinusoidalOscillatorsUsingCFOAs. . . . . . . . . . . . . . . 131
5.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
5.2 TheEvolutionofSingleElementControlled
Oscillators:AHistoricalPerspective. . . . . . . . . . . . . . . . . . . . . . 131
5.3 AdvantagesofRealizingWienBridgeOscillator
UsingCFOAvis-a`-visVOA. . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
5.4 Single-Resistance-ControlledOscillators(SRCO)
UsingaSingleCFOA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
5.4.1 ANovelSRCOEmployingGroundedCapacitors. . . . . . . 138
5.5 Two-CFOA-Two-GCSRCOs:TheSystematic
StateVariableSynthesis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
5.6 OtherTwo-CFOASinusoidalOscillatorTopologies. . . . . . . . . . . 143
5.7 DesignofActive-RSRCOs. . . . . . . . .. . . . . . . . .. . . . . . . . .. . 148
5.7.1 Active-RSinusoidalOscillatorsUsingCFOA-Pole. . . . . . 148
