SURE: Shizuoka University REpository http://ir.lib.shizuoka.ac.jp/ Title Author(s) Citation Issue Date URL Version Class A CMOS Current Conveyors Watanabe, Kenzo; Cha, Hyeong-Woo; Ogawa, Satomi IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences. E81A(6), p. 11641167 1998-06-25 http://hdl.handle.net/10297/3442 publisher Rights This document is downloaded at: 2015-02-01T00:47:18Z IEICETRANS．FUNDAMENTALS，VOLE81−A，NO・6JUNE1998 1164 LETTER SpeciaI SecIfonofPaperざSe庇kd加mJm・CSCC’97 CIassACMOSCurrentConveyors Hyeong・WooCHA††SatomiOGAWA†，andKenzoWATANABE†，MembeTT SUMMARY Thesecond−generationCMOScurrentconveyors aredevelopedforhigh−frequencyanalogslgnalprocesslng・Itconsists ofasourcefollowerforthevoltagelnPutandaregulatedcurrentmir− rorbrthecurrentlnPutandoutput・ThevoltageandcurrentlnputStageS arealsocoupledbyacurrentmirrortoreducetheimpedanceofthe currentlnputPOrt・Simulationsshowthatthisarchitectureprovidesthe bythenegativefeedback，butthebandwidthisstillcompa− rabletothatofanop−amp・Thiscomparisonofkeyperfor一 mancefeaturesimpliesthatanidealCCIIcouldberealized byapplyingthenegativefeedbacktothepush−pullarchitec− ture．Basedonthisidea，aneWarChitectureofCCIIisdeve1− highinput／Outputconductanceratioandtheinherentvoltageandcur− opedl20］．ComparedtotherecentlyproposedCCIIwhich renttransferbandwidthsextendingbeyondlOOMHz・Theprototype usesacascodestagetokeepthepotentialatthecurrentlnput chipsfabricatedusingO・6pmCMOSprocesshaveconnrmedthesimu− 1atedperR）rmanCeS，thoughthevoltageandcurrentbandwidtharelim− itedto20MHzand35MHz，reSpeCtively，bythebuilt−incapacitances nodeconstant【21］，thisarchitectureusesthefeedbackstage l．Introduction whichconsistsofasimplecurrentmirror・Theoperationof thefeedbackstageisindependentofthebiascurrentandthus itisapplicabletoclassABCCIIs・InthefollowlngS，itscir− cuitconfiguration，SimulatedandmeasuredperformanCeSOf theprototypechipsfabricateduslngO・6pmCMOSprocess willbedescribed． Acurrent−mOdeapproachisqulteattraCtivetohigh−frequency 2．CircuitDescription Ofthebondingpads・ 恒…川か．・川′・′川卜川り‘／川．岬／／り…血糊。∫lJり・ゝMJ‘●．叩JHJ（、わ＝址 （Ⅵr／で〃Jco／ZVり’Or slgnalprocesslng，becauseitcanberelievedofthegain−band− WidthlimitationaccompanylngWiththevoltage−mOdeslg− nalprocesslng・Aversatilebuildingblockforcurrent−mOde slgnalprocesslnglnthecontinuoustime−domainisthecur− rentconveyor［1日2］．rIbwarditsmonolithicimplementa− FigurelshowsthecircuitdiagramoftheCMOScurrentcon− veyor・TransistorM2，M3・M4，andM6formtheregulatedcur− rentce11forthecurrentlnPutandMlformsthesourcefo1− lowerfbrthevoltagelnput・M3，M5，andM7formthecascode tion，manyarChitecturesofthesecond−generationcurrent currentmirrortotransferthecurrentiflowlnglntOthenode conveyors（CCIIs）basedonop−amPSfollowedbycurrent XtothenodeZ・AssumefbrthemomentthatM3，M4，andM5 mirrorshavebeenproposedintheearlystageofdevelop− andtwocurrentsourcesJarematChed．Then， ment【3］．Theseevolutionaryarchitecturesandtheirapplica− tionshavehappilyprovedthatanyfunctioneverperformed J＿＝上．r． （1） inthevoltagedomainispossiblewiththecurrenトmodeap− ThesameamountofthecurrentalsoflowthroughMl・There− proachl4］，buttheirperformanceshavefailedtosurpasstheir fore，thefollowlngrelationholds・ voltage−mOdecounterpartsl5日7］・ Current−mOdeprocesslngftaturesinherentwideband− widthcapability・Tbfullyeruoythisadvantage，theinnova− tivearchitectureofCCIIhasbeenexploitedandmanyarchi− tectureswhichdonotinvoIveop−ampShavebeenreported・ Thoughdifferentindetails，theirlnPutStageSCanbeclassi− fiedintotwobasicarchitectures；Onebasedonthepush−pull gml（V、、一再＝g証−VJンVダム．、， （2） wheregm，（i＝1，2）isthetransconductanceofMi，Vsisthe sourcepotentialofMl，andRistheloadresistorconnected tothenodeX．From（2），Wehave stagederivedfromtheWilsoncurrentmirror【8］−［14］and theotheronthedifferentialstagel15日19］・Intheformer configuration，thewidebandvoltageandcurrenttransferchaト acteristicsareaChievable，butthefiniteimpedanceatthecur− rentlnPutPOrtinvalidatesthevirtualgroundconcept・Inthe latterconfiguration，Ontheotherhand，theimpedanceatthe currentlnPutpOrtCanbereducedtoanegligiblysmallvalue ManuscrlptreCeivedOctoberl，1997・ ManuscrlPtreVisedDecember26，1997・ †TheauthorsarewiththeResearchInstituteofElectronics， ShizuokaUniverslty，Hamamatsu−Shi，432−8011Japan・ Fig・1ThecircuitdiagramofCCII＋・ LETTER V ＝ g研lg′〃2凡V、， ■r gml一g川2＋g′扇乳〃2年で （3） Ifgm．＝gm2，Orgm．gm2年r》g”，．て〝，，Whichisreasonableinprac− ④，reSPeCtively・AmicrophotographoftheCCII＋issh。Wn inFig・3・AllPMOStransistorscanbeseenimplantedinto then−WellintheupperpartexceptMっwhichisimplanted independentlylntOthen−Wellinthelowercentralpart．Per− fbrmancesoftheseprototypechipsweremeasuredunderthe tice，thenvfollowsexactlyvY・Theoutputimpedancer＝is biascondition；㌦。＝」ts＝2・5V，th＝−0・5V，andJ＝100日A ㌔＝㌦〟（g用石打㌔6）， （4） WhereristheinternalresistanceofthecurrentsourceJand ㌦i（i＝5，7）isthedrain／sourceresistanceofM，・Ifthecurrent WhichwassetbytheextemalresistorconnectedbetweenNl andtts・Measuredperfbrmanceswerecomparedwiththose SimulateduslngHSPICEwithleve147transistormodel． Figure4showsthecurrent−VOltagecharacteristicsatthe i＝isnotafftctedbytheload・Nocurrentflowsthroughthe nodeXwhennodesYandZareshort−Circuited・Theinput impedancerrandtheoffsetvoltageatnodeXare350Qand nodeY；iY＝0・TheinputimpedancerratthenodeXisglVen −0・43V，reSPeCtively・Thesemeasuredvaluesdifftrlargely SOurCeJconsistsofthecascodemirror，thenr＿issohighthat by fromthosesimulatedones，30f2and−0・33V・reSPeCtively・ Thedifferencesareattributedtoincorrectbody−effect paramters・Introducingthediode−COnneCtedPMOS and 1 g，，河g′痛 1 r ＝−− NMOStransistorsinserieswithMlandMっ，reSPeCtively，One ’rg椚2g諸道g′痛＋‰ （5， Inderiving（5），gminsi》lisassumed．Thesecondterminthe right−hand−SidearisesfromthecascodecurrentmirrorR）rmed byM3，M4，andM6WhichregulatesthesourcevoltageofMっ・ Withtheproperdesignoftheregulatortheinputimpedance rrcanbemadenegligiblysmallandthenodeXisvirtually CangreatlyreducetheoffSetvoltagel19］．Figure5showsthe CurrenttranSftrcharacteristicsbetwee中、andi＿Whenthenode Yisshort−CircuitedandthenodeZisvirtua1−grOundedbythe Thblel TtansistordimensionsinCCIIs． T ra n sisto r W 叫 m ） M ． 30 M ， 12 0 M l、 M 、 40 3 M b 、 M IJ 60 1． 8 M N 、 M 1日 50 1． 8 M 二言 30 1． 8 groundedwhenvY＝0・ SummanZlngthecircuitoperationsdescribedabove，One CaneXPreSStheinput−OutPutrelationsasfbllows： V 、 ・ LV I 、 0 0 0 0 0 1 0 1 0 ・㌔ V了し、 M ” L叫m ） 1． 8 1． 8 （6） Thismatrixrepresentationindicatesthatthecircuitshownin Fig・1istheCCII＋itself・TheCCII−Canberealizedbyin− Vertlngi−bymeansofacross−COuPledcurrentmirror． 3．Pern）rmanCeS TheCCII＋andCCII−basedonFig・lwerefabricateduslng O・6pmCMOSprocess・Thecompletecircuitdiagramis ShowninFig・2andtransistordimensionsarelistedinThble l・TheterminalconnectionshowninFig・2isfbrtheCCII＋． FortheCCII−，terminals④and⑥areconnectedto③and Fig・3 AmicrophotographofCCII＋． し ′ し ′ llT ／ ＼ C C lト ！ −100 −50 0 50 100 Fig・2 ThecompletecircuitdiagramofCCIIfabricatedusingO・6Hm CMOSprocess． ん［ト止】 Fig．4 TheinputcharacteristicsatthenodeX． IEICETRANS・FUNDAMENTALS，VOL・E8lTA，NO．6JUNE1998 1166 TbbIe2 MeasuredperformancesofCCITs． C lass A C C H ＋（ C C Jl− ） m e Sured UUIl＋ ／ ■ ； ■ ， ヽ ‖ l＿ ◆ ■ 1 ＼ CC Iト −100 −50 0 50 100 150 ／X［ト止］ Technology 0・ 叫 m n− W e11C M O S process Supply voltage 5 V or ＋ 2． 5 V to T2 ． 5V Pow erdissIPation 2mW （ 3m W ） Im pedance atnode X 350 n 1m pedance at node Y n lm p e danee at node Z 6Mn O ffset voltage （ V、VS・ V、 ） − 0． 43 V O ffsetcurrent（ ilVS・ i） l・ 9 PA （ 1． 1ト lA ） V oltage dynam ic range − 0． 5 V to ＋1． 5V C urrent dynam ic range − 100 ト IA to ＋150 いA 3− d B cutoff frequency of （ V／V） 2n M H z W hen R ＼ ＝1O kO 3− dB eutoff frequency of （ V， ／ vl・ ） 18 M H z W hen R ヽ ＝ ′ R ＝10 kf2 Fig．5 Thei＿VS．iLCharacteristics． 冨P︺ u橋口 0 5 0 5 0 5 2 1 1 − l l 3− dB cutofffrequency of（ jZ／ jJ 35 M H z A ctive chip area 0． 2 ×0． 2【 mmコ 】 ） l CCII＋．Themeasuredbandwidthis35MHzwhereasthesimu＿ 嘉 † J u inthefrequencyresponsebetweensimulationsandmeasure− 全 l ＝ r y l l 」 mentsinFigs・6and7areattributedtotheparasiticpoles ヽ l 1 Createdbythestraycapacitanceofthebondingpadswhichis nottakenintothesimulation・Thepadcapacitanceisesti− l ヽ ヽ ヽ 1 ＼ R latedbandwidthextendsbeyond300MHz．Thesedifftrences matedexperimentallytobe15pF・Figure6alsoshowsthe frequencycharacteristicsofCCII＋whenusedasavoltage amplinerwithnodesXandZterminatedby2kf2and10kfl， respectively．The−20dB／decaderol1−0ffcharacteristicsindi＿ 1．E＋031．E◆041．E十051．E＋061．E◆071．E＋081．E＋091．E◆10 Catethatthebandwidthislimitedagainbythepadcapaci− tances・rIbconfirmtheseexperimentalobservation，thefre− Frequency［HZ】 Fig・6 Thefrequencycharacteristicsofthevoltagetransferfunction． quencycharacteristicsincludingthepadcapacitancesare l Characteristicsandalsoconfirmthatthehighfrequencypeak− lngapPearlnglnthefrequencyresponseofthecurrenttrans− Simulated・Theresultsareingoodagreementwithmeasured ⊥ l 1 1 − 1 5 0 ︻宅］ヾ＼ヾ l l l † T rl l ‡ ＼ t l ferfunctionisduetothepadcapacitances．Thesamefre− quencyresponseswerealsoobservedinCCII−． 4．Conclusions CircuitconfigurationsandperfbrmancesofCCIIsfabricated uslngO・6HmCMOSprocessweredescribed・Measuredper− formancesaresummarizedinTbble2・Theseperformances， 1．Eペ）31．E＋041．E＋051．〔＋061．【＋071．E＋081．E＋091．〔十10 especiallythebandwidth，areinsufficientforenJOylngCur− Frequency［Hz］ rent−mOdeslgnalprocesslng・Thedominantpolewhichlim− itsthebandwidthisformedbytheparasiticcapacitancesof thebondingpadsandextemalresistors．Therefbre，theband− Fig・7 Theftequencycharacteristicsofthecurrenttransfbrfunction． Widthcanbegreatlyextendedbyloadingtheoutputnodes Current−tO−VOltageconverteruslnganOp−amP・Agoodagree一 mentbetweenthesimulationandthemeasurementandthe linearcurrent−fbllowlngaCtionoverthefullbiascurrentrange Canbeseen． Figure6showsthefrequencycharacteristicsofthevolt− Withsmallresistors・Anotherissuefbrhigh−aCCuraCySlgnal PrOCeSSlngisthelargeoffsetvoltage・Simulationsshowthat theoffsetvoltagecanbegreatlyreducedbytheinputstageS COmprisedofCMOSpalrS・Theseimprovementsarefuture WOrkstowardanidealCCII． agetransferfunctionofCCII＋WhenthenodeXandZare loadedby2kE2・The−3dBcutofffrequencyis20MHz・Ac− Rettrences COrdingtosimulationswithoutpoundingpads，theinherent bandwidthextendsbeyondlOOMHz・Figure7showsthefre− quencycharacteristicsofthecurrenttransferfunctionof 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