基于单片机的数字时钟设计--外文翻译(3)

10.2.2.2DeviceSimulation

Atwo-dimensionaldevicesimulator,handlingbothsignalelectronsinabulkpoten-tialwellandholecurrentalongthesilicon–silicondioxideinterfacesimultaneously,hasbeennewlydevelopedtoanalyzethe oatingsurfacedetector.Thesimulationsweredonealongthesignalelectrontransferdirection.Figure10.11a,bshowsthepotentialdistributionsfornosignalchargeandfor3600-electronsignalcharge,respectively.ThepotentiallevelatyD0inFig.10.11indicatesthesurfacepotential.The rstmaximumpotentiallevelalongtheyaxisindicatestheburied-channel

Abstract Virtually complete charge transfer can be achieved with charge coupleddevices(CCDs)intheburiedchannelconfigurationbecausetheburiedchannelCCDintroduces no transfer noise. However, conventional charge detectors incorporatedinto CCDs have a comparably large noise, which consists of thermal noise and 1/fnoisefromMOS transistorin theoutputchargedetectors.

228Y.

MatsunagaFig.10.11Two-dimensionalpotentialdistributionatdetectionsection.(a)Nosignalelectron.(b)3,600signalelectron

potential.AsshowninFig.10.4b,thesurfacepotentialinthedetectorsectionisloweredbysignalcharge,comparedtothatfornosignalcharge.ThesensingcapacitanceiscalculatedwiththeamountofsignalchargeandthedifferenceinthesurfacepotentialsbetweenFig.10.11a,bwhichcorrespondstothecharge/voltageconversiongainofthedetector.Theresultantsensingcapacitanceis0:22fF= mperFPPlength.

10.2.2.3Evaluation

Thedeviceisevaluatedata7.16-MHzclockfrequency,whichistwicetheNTSCcolorsubcarrierfrequency.Thesignalduty,whichisthesignaloutputperiodtotheclockcycletimeratio,isapproximately75%,whichwasdeterminedbya35nspositiveresetpulse.Themeasuredcharge-to-voltageconversiongainofthisdetectorisshowninFig.10.12asasolidline.Itwasmeasuredbyinjectingaseriesofchargepacketsintothesensingchannel.Theconversiongainislinearoverachargepacketrangefrom20to4,500electrons/packet,anditisashighas220 V/electron.Themeasuredconversiongainishigherthanthatobtainedfromthesimulatedsensingcapacitancevaluebyabout20%.Athree-dimensionaldevicesimulationmaybeneededformoreaccurateestimation,becausethedifferencebetweenthemeasurementandthecalculationcanbeduetopotentialdistributionperpendiculartothesignalelectrontransferdirection.

Theoutputnoiseofthenewdetectorwasmeasuredusingaspectrumanalyzer.Figure10.13showsnoisespectraforthedevice,bothintheresetoperationandinthetransferoperation.Intheresetoperation,residualchargeinthesensingchannelincludesresetnoise(kTCnoise)chargeduetothethermalnoisegeneratedintheresetgate(RS).Conversely,inthetransferoperation,theresetnoiseiscompletelysuppressed,becausenoresidualchargeexistsinthesensingchannel.Theoverall

Abstract Virtually complete charge transfer can be achieved with charge coupleddevices(CCDs)intheburiedchannelconfigurationbecausetheburiedchannelCCDintroduces no transfer noise. However, conventional charge detectors incorporatedinto CCDs have a comparably large noise, which consists of thermal noise and 1/fnoisefromMOS transistorin theoutputchargedetectors.

10Low-NoiseElectronicImagingwithDouble-GateFETs

Fig.10.12Charge/voltage

conversioncharacteristics

1

Output voltage [V]22910-110-210

-3

10-4

1101102103104

Number of electrons

[electrons / packet]

Fig.10.13Noisespectraof

oatingsurfacedetectorin

resetoperationandintransfer

operation

rmsnoisevalue,withinthefrequencyrangeof10kHz–3.58MHz,is84 Vrmsatroomtemperature.

Thenoiselevelof84 Vrmsandasignaldutyratioof75%resultinaneffectivereadoutnoiseofaslowas0.5electron.Thus,thedynamicrangeisaswideas79dB.Inthesignalrangebelow20electrons,chargegenerationbyphotoelectricconversioneffectintheCCDwithweakincidentlightthroughaneutraldensity(ND) lterisinducedtoevaluatethedetector,asshowninFig.10.14.Injectionpacketsizeinthesensingchannelisknowninadvancebythismethod.Asignalpacketoftenelectronsismadebyinsertinga10 2ND lterinthelightpath.Thelightintensityissetsoastogenerate1,000electrons/packet,whichismeasuredusingthecurrentmeterinthe gure.Figure10.15ashowswaveformsoftheRSinputpulse,a¥1inputpulse,andtheresultantoutputsignal.Figure10.15bisa

Abstract Virtually complete charge transfer can be achieved with charge coupleddevices(CCDs)intheburiedchannelconfigurationbecausetheburiedchannelCCDintroduces no transfer noise. However, conventional charge detectors incorporatedinto CCDs have a comparably large noise, which consists of thermal noise and 1/fnoisefromMOS transistorin theoutputchargedetectors.

230Y.

MatsunagaFig.10.14Evaluation

circuit

Fig.10.15Charge/voltageconversioncharacteristics.(a)RS,®1input,andresultantsignaloutput.(b)Ampli edoutputvoltagearoundtensignalelectrons

photographofthesignalvoltageampli edbyanexternalcircuitwhentheaveragenumberofelectronsinasignalpacketis10.Theampli edsignalisprocessedthrougha3.58MHzlow-pass ltertoremoveworthlesshigh-frequencynoise.Discretevoltagelevelscorrespondingtoaroundtenelectronsareobserved.Outputlevels,whichcorrespondtootherthantenelectrons,arecausedby uctuationoftheincidentlight.Thecharge-to-voltageconversioncharacteristicsobtainedbyobservingthediscretelevelsareshowninFig.10.16.Theconversiongainabove10electronsinFig.10.16isapproximatelythesameasthatinFig.10.12.Theconversionratioundertenelectronsshowslesslinearity.However,highresponsivityisstillmaintainedinthesmallsignalregion.

Abstract Virtually complete charge transfer can be achieved with charge coupleddevices(CCDs)intheburiedchannelconfigurationbecausetheburiedchannelCCDintroduces no transfer noise. However, conventional charge detectors incorporatedinto CCDs have a comparably large noise, which consists of thermal noise and 1/fnoisefromMOS transistorin theoutputchargedetectors.

10Low-NoiseElectronicImagingwithDouble-GateFETs231

Output voltage [mV]21

0510

Packet size [electrons]15

Fig.10.16Charge/voltageconversioncharacteristicsobtainedbydiscret …… 此处隐藏：6382字，全部文档内容请下载后查看。喜欢就下载吧 ……