第1章-器件

1SENANJINGwujinChapter1Chapter1Dev[e-mail]-II,2012,092SENANJINGwujinCircuits(Circuits(NetlistNetlist)=Elements+Connection)=Elements+ConnectionWhatisElectronicCircuits?ElementsStructure&itsOperationState(Behavior)-Active/Passive;基本结构属性-linear/Nonlinear;信号处理属性-Small/LargerSignal;工作条件属性-Connection(Condition).典型应用属性Elementsordevices:PrimaryorBasicCellinthecircuit元器件在电路中的基础地位和决定性作用元器件的选择+连接关系(结构)+参数(量化)3SENANJINGwujinActive:Active:有源有源,variable,variable••PNJunctionPNJunction••BJTBJT••MOSFETMOSFETPassive:Passive:无源无源,simple,simple1.1.ResistanceResistance2.2.CapacitanceCapacitance3.3.InductanceInductanceElements(Devices)Passive:Twoterminals;linear;Biasingunnecessary;toprovideactivedevicesoperationpoint(Biasing).Active:ExceptDiode,threeormoreterminals(Why?)Staticbiasingnecessary,Generallynonlinear;linearonlyundersmallsignalapproximation(Math.)Onlyactivedevicewithmorethantwoterminalscanbeusedinamplifying,andseriousconditionsneededforlinearamplification.4SENANJINGwujinPassive:LinearResistancePassive:LinearResistanceApplication,VtoI:•BranchCircuitCurrentdefinition;•CurrentBasing.GoodinVLSIApplication,ItoV:•CurrentLimiting;•CurrentSensing;•VoltageBasing,PoorinVLSINRWLddWLSLRS×=×=⋅==ρρρLinearresistance,Ohmlaw:V=I×R选择电阻类型(结构/材料:RS),设计图形(N)电阻自身的设计简单,主要考虑在电路中的电流定义、电位调节，设定合适的工作点和匹配条件！5SENANJINGwujinPassive:LinearCapacitance&InductancePassive:LinearCapacitance&InductanceCapacitance:)(00LWtSCCoxox×==εεC和L功能上表现为对偶特性Lagersignal&timedomain描述Smallsignal&frequencydomain描述电容上电压不能突变,电压纹波电感上电流不能突变,电流纹波IdtdVCC=CjXCω1=Applications:时域大信号:Start-up,PulseOSC,Delay,DCseparator;频域交流小信号:SinusoidOSC,LoopCompensations,FilterLLVdtdiL=LjXLω=Inductance:0LLl=均为储能滤波元件,C:Easyinintegration,L:DifficultinintegrationIC中至少C不可避免,电路频率、特性、瞬态特性和稳定性问题(相移)产生的根源！6SENANJINGwujinSimplestactiveelement:PNJunctionSimplestactiveelement:PNJunction电流性质--扩散电流,I-V指数规律,V-I对数率,显著非线性)exp(]1)[exp(00TPNSTPNSPNVVIVVII≈−=kmVqkTVT300@26≈=Question:PN结在电路里有何具体应用?直流：隔离，稳压，钳位，电平移位；交流：低阻高频极点、交流短路，结电容变容效应；拓展应用：MOSDiode电流镜)ln(0SPNTPNIIVV≈IS0反向饱和电流与反偏电压无关,但随PN结面积而增大PN/Diode--正向导通(电压近似钳位),反向截止直至击穿⇒热电压,理想正温度系数电压电子能量7SENANJINGwujinActive:BipolarJunctionTransistor(BJT)Active:BipolarJunctionTransistor(BJT)结构:两个背靠背PN,发射结正偏,集电结反偏;三端口,非线性电流性质:本质上仍是PN结电流!发射结正偏提供扩散电流Ie;基极复合形成IB；集电结反偏对Ie按比例收集,形成IC;1.VBE正偏,有IE注入;2.VCB正偏或零偏,收集系数随偏压线性变化,导致IC随反偏电压线性变化;3.VCB反偏,收集系数逐渐趋向饱和,昀大为1饱和的昀大收集系数导致IC电流饱和.)exp(0TBECCVVII≈CEBIII−=Question:画出BJT输出特性曲线,与MOS输出特性比较?形似而内在机制不同,应用可类比、借鉴！8SENANJINGwujinActive:MOSFET(MetalActive:MOSFET(Metal--OxideOxide--Semiconductor)Semiconductor)本质:强反型下为漂移电流,Ω定律成立(修正),弱反型下为扩散电流；性质:漂移电流线性律;饱和限流/恒流),扩散指数律(进入-成为非线性)增强型?耗尽型?特点:PN结反偏天然隔离(衬底);纵向:平板电容,横向:对称原理:栅压(纵向电场)感应电荷，形成反型沟道、沟道电阻(开启)漏压(横向电场)驱动沟道电阻,形成沟道电流;两维电场FourTerminals:Gate(G),Source(S),Drain(D),Substrate(Bulk)9SENANJINGwujinDimension:WidthLengthRatio(W/L)NMOSStructure:TwoDimensionalElectricalFieldPlateCap,ControlledResistor工艺规范制造,设计确定形状和尺寸简单看就是压控可变非线性电阻10SENANJINGwujinDeviceSymbol:twostyleVoltageControltype(logic)Currentdirectiontype(Analog)DefinitionDrain&Source•Physical•Circuit(CurrentDirection)NMOS:DtoSPMOS:StoDPMOS:s/bulk,high,VDD,NMOS:s/bulk,low,VSSSubstratePotential?-ReverseBiased,抑制衬底PN结电流！P:方向向外;N:向内Drain:N/PMOSConnectedpossibleDSGGDSSource:提供载流子;Drain:收集载流子11SENANJINGwujinMOSFETDCpropertiesI-Vequationsindifferentregion;DCParametersinMOSFET.12SENANJINGwujinDCCurrent:InducedCharger(NMOS)DCCurrent:InducedCharger(NMOS)()xoxGSTHxdQCVVVWdx=−−oxoxoxtCεε0=ChargerinChannelinducedbyGateVoltage(dxwithVx),非均匀TotalQinvinChannelinducedbyFieldEffectLinearapproximationofVxaroundLxDSDSxdVVLdxVLxV==,00()1[()]2DSLVinvxoxGSTHxxDSoxGSTHDSWLQdQCVVVdVVCWLVVV==−−=−−∫∫0;SDDSVVV==VTH:阈值电压,有源器件都有一个开启电压,VBE,VTN,VTPGSTHVV≥,GDTHDSGSTHVVorVVV≥≤−13SENANJINGwujinDCCurrentindifferentregionDCCurrentindifferentregion2invinvDSDSinvinvQQVIQEQtLLLυμμ====Carriermoving:DriftundertheElectricalFiled,mobilityμLVEELtDS===,,μυυLinearCurrent,ΩLow1()DSdsDSVRonIk=≈×Δ21[()]2DSoxGSTHDSDSWICVVVVLμ=−−DriftCurrent21()2DSDSDSIkVV=Δ×−2,1,2DSsatGSDSGDTHIkVVVV=×Δ−==Definition','(/),oxGSTHkCkkWLVVμ==Δ=−过驱动线性电流→饱和漏电流导通电阻14SENANJINGwujinParametersDefinition&SecondaryEffectsParametersDefinition&SecondaryEffects'kProcess/GainfactorWidth-LengthratiokOverdrivevoltageΔThresholdVoltageTHV/WL)22(0fBSfTHTHTHVVVVϕϕγ−+=−=ΔSubstratebiasingcoefficient02/SisuboxqNCγεε=Explain:QB↑→Qinv,eff↓→VGS↑→ΔVTH↑AC:背栅跨导衬底偏置效应(DC)Usuallyinversebiased,NMOS:VBS0;PMOS:VBS0沟道调制效应21(1),,2DSDSDSGSTHIkVVVVλ=×Δ+≥Δ≥MOSFET更关注在饱和恒流区的应用-不可替代性15SENANJINGwujin沟道调制效应沟道调制效应––对饱和漏电流修调的由来对饱和漏电流修调的由来)1()1(DSeffVLLLLLLLλ−=Δ−=Δ−=()(1)(1)(1)DSeffDSDSAλλ=≈+=+−引入沟道调制系数λ,理想λ→0;等效厄利电压VA,理想VA→∞LVVVAAA0,1==λ22,11(1)(1)22DSDSsatDSAVIkVkVλ≈Δ+=Δ+实际输出电流与VGS,VDS两种电压均有关;VGS(主控),VDS(辅控);I-V:线性率-平方率(含修调),大信号表现出强烈的非线性.LWLW⇒)(effLVVAA=0沟道漏端空间电荷区使有效沟长下降等效W/L增加MOS:电压控制电流源,VoltageControlCurrentSource(VCCS)16SENANJINGwujinOperationregionDiscussionOperationregionDiscussion强反型基本条件:VGSVTHorΔ01.线性电阻区VDS≤VGS-VTHorΔ≥VDSD端沟道未夹断,VGD=VG-VD=VGS-VDSVTHVDS→0,均匀沟道电阻,非线性消失,理想线性电阻工