基于单片机的数字时钟设计--外文翻译(8)

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.

226Y.Matsunaga10.2.2FloatingSurfaceType

Analternativelow-noiseandwidedynamicrangechargedetectorcalled“double-gate oatingsurfacedetector”differsfromthe oatingwelltypeinthattheP-channelFETcurrent owsatthesilicon–silicondioxideinterface.Anadvantageofthistypeisitshighconversiongainduetothesmallsensingareacomparedtothe oatingwelltype.Thedeviceachievesacharge-to-voltageconversiongainof220 V/electronandadynamicrangeof79dBat3.58MHzvideobandwidthandatroomtemperature.Thisdetectorshowsaneffectivereadoutnoiseofonly0.5electronsrms,sothatitcanbeusedasanelectroncountingdetectorandtheevaluationcanbedonebydirectlyobservingthediscretelevelscorrespondingtothenumberofsignalelectrons.The79dBdynamicrangeissuf cientforaCCDimagesensordetector.

10.2.2.1DeviceStructure

ThedevelopedchargedetectorhaslowsensingcapacitanceandastructurewhichisinherentlyfreeofkTCnoise.Theprincipleisacombinationofann-typeburiedsensingchannelandaP-channelsurfacedetectiontransistoracrossit[5–7].Figure10.9showsacross-sectionalviewofthedetectiontransistoracrossthesensingchannel.Ashallowp-wellwithasensingchannelinitandsource/drainpCregionsareformedonann-typesubstrate.Theshallowp-wellunderasensingchanneliscompletelydepleted.TheP-typechannelforthedetectiontransistorliesatthesilicon–silicondioxideinterface.ThechargepacketsmodulatethechannelconductanceintheP-channeldetectiontransistor.

SGD

Sensing channel

Fig.10.9Crosssectionof oatingsurfacedetectiontransistor

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