cmos模拟集成电路设计视频教程-东南-配套第1章

ogIC

Chapter1Devices-MOSFETVersion-II,2012, WhatisElectronic

Circuits(Netlist)=ElementsElementsordevices:PrimaryorBasicCellinthe元器件在电路中的基础地位和决定性元器件的选择+连接关系(结构)+参数(量化ElementsStructure&itsOperationStateSmall/Larger

Elements(

Active有源PN

Passive无源simplePassive:Twoterminals;linear;BiasingtoprovideactivedevicesoperationpointActive:ExceptDiode,threeormoreterminals(Why?)Staticbiasingnecessary,Generallynonlinear;Onlyactivedevicewithmorethantwoterminalscanbeusedamplifying,andseriousconditionsneededforlinear Passive:

,Ohmlaw:RL LR W 选择电阻类型(结构/材料:RS),设计图形Application,VtoBranchCircuitCurrentCurrentBasing.GoodinApplication,ItoCurrentCurrentVoltageBasing,Poorin

电阻自身的设简单, 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 Passive:LinearCapacitance&

CCS

(W

Inductance:LLt tC和L功能上表现为对偶特

CdVC

L

Lagersignal& 描Smallsignal& 描

XC

XL电容上电压不能突变,电压电感上电流不能突变,电流纹

IC中至少C不可避免,电路频时域大信号Start-upPulseOSCDelayDC Simplestactiveelement:PN PN/Diode--正向导通(电压近似钳位),反向截止直至击穿电流性--扩散电流,I-V指数规律V-I对数率显著非线性 )1] Vln(IPN S

S

SIS0反向饱和电流与反偏电压无关,但随PN结面积而增热电压,理想正温度系数电

kT26mV@ 电 能Question:PN结在电路里有何具体应用直流 ，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 Active:BipolarJunctionTransistor

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；IBIE集电结反偏对Ie按比例收集,形成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

exp(VBEV CV CQuestion: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

FourTerminals:Gate(G),Source(S),Drain(D),Substrate特点:PN结反偏天 横向:对原理: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;两维电场增强型耗尽型本质强反型下为漂移电流定律成立(修正弱反型下为扩散电流； Dimension:WidthLengthRatio

工艺规范制造,设计确定形状和尺PlateCap,Controlled

简单看就是可变非线性 DeviceSymbol:two

VoltageControltype Currentdirectiontype Substrate-ReverseBiased,抑制衬底PN结电流P:方向向外;N:DefinitionDrain& Source:提供载流子;Drain:收集载流Circuit(CurrentPMOS:s/bulk,high,NMOS:s/bulk,

NMOS:DtoPMOS:StoDrain:N/PMOS

DCI-Vequationsindifferentregion;DCParametersinMOSFET.

DCCurrent:InducedCharger ChargerinChannelinducedbyGateVoltage(dxwithVx

Vx

LinearapproximationofVxaroundxVx ,dxLx

0;

TotalQinvinChannelinducedbyFieldL dQ

VDS

V)WL

VGDVTH xC )1 x

VGS

DCCurrentindifferent

ElectricalFiled,mobility

tL,

ELDrift

EQinvVDS

inv

LinearCurrent,

W 1V2 kCox kk'(W VGS 过驱 k(V 1V2

导通电阻 (on)VDS

k线性电流饱和漏

1k2, DS

Process/Gaink

Width-LengthW/

Overdrive

Threshold衬底偏置AC:背栅

VTHVTHVTH0 2f2q2f2q0Si

2/2Explain:Usuallyinversebiased,NMOS:VBS<0;PMOS:沟道调制效

1k2(1 ), ,

MOSFET更关注在饱和恒流区的应用-不可替代 沟道调制效应–对饱和漏电流修

LLL(1L)L(1 等效W/L

(W W(1 )W(1VDS L(1 引入沟道调制系数,理想等效厄利电压V,理想V

1,

A(W

1k2(1 )

1k2(1VDSA DS A实际输出电流与VGS,VDS两种电压均有关;VGS(主控),VDS(辅控 非线性

Operationregion

工作区域的限定与两VGS:截止-弱反型(亚阈)-过渡-强反型；VDS:线性-过渡-D端沟道未夹断,VGD=VG-VD=VGS- 饱和恒D端沟道夹断VGDVTHVDSVGS-VTHVDSVDS到达临界点后,多余VDS降落在漏漏耗尽层中,沟道电阻形状不变,漏收集电流系数饱和为1,电流近似恒定.

OverdriveVoltage

饱和

1

2IDSk2IDSkQuestion:=0时电流IDS=0或者说,强反型饱和电流模型在当IDS0时,一定可进入弱反型亚进入过渡区和亚阈区后,可使0甚至<0Question:如何判断在弱反型下的漏饱和恒流临界条件

SubthresholdorWeak -100mV左两种电流成份并存:VGS感应的载流子梯度形成VDS横向电场驱动形成漂 exp(VGSVTH)[1exp(VDS 当VDS>>3VT时,浓度梯度大,但载流子总量小，扩达到输出电流饱和条件 栅控电压调制为主的扩散电流分

)Iexp(VGS D

SimilartoBJT,亚阈的MOSFET可视为BJT(I-V功能特性)观特征:电流小,或小电流易工作WI区,n>1亚阈斜率

ACRelated&ComefromDCACParametersinMOSFET:Small

AC

ACparametersarederivedbyDCI-V AC:gm&栅压、漏压对输出小

io1

线性

@

Constan

d d

@VGSConstan

io

线性叠交流参数与直流I-V方程有关,由直流工作点定义最关心饱和区的交流参数 存在gm和gd的非对称,可放大?

gm&gdunbalancedforpossible

gm(SI)k

2I

k

I

1

&

大信号下一定产生非Whatis

/2

VA0L 高

IDS

恒流信号放大:定性/定量

io

gmgd

gm/

Review:MOSFETOperation Digital:x-yTurn-on；Cut-yx

og:x-y第一象Turn-CurrentVoltageStrong/Weak og:R,ConstantI,Constant

MOSDiode:VoltageSource 饱和/线性临界线右平移类似PN结I-V定T T

r1

低

gm

恒压 VDSVGS1

m m

输出阻抗转变恒流恒压o oSmallSignalEquivalent 低频等效电路,忽略电容栅-源电栅-漏覆盖(Miller)电容漏-源输出(负载)电容MOSDiode:G-D短路,gmVgs=gmVds受控源等效1/gm总输出导纳gT=gm+gd,总输出阻抗Question:IsLreductionreallybenefit ogNegative:LroGainPositive:LCgsfT

io Vgs

小尺寸,精度

fT

Twotransistors:Parallel&

(W

(L

)M1L

L)M

(W/ (W/同类MOS串、

Large

M M

Exe:利用等效W/L,判断MA,MB状态Result:MB:Saturation;MA: 定义法证明,或复合管等效W/L法证明Alwaystruewithoutrelatedwithtwo复合管:一个MOS管拆分为若图形尺寸效应:W/L相同的复合管和单有差异！W/L相同但W,L不同的单管有差异 Discussion:Operationstatues

HowcanaMOSFETinCircuitwithazeroCut-off,VGS<<VTH,SwitchTurn-on,VGS>VTH,VDS=0,similarasRwithThesaturatedcurrentisalwayslargerthanthelinearcurrentTrue,ifVGSfortwotransistorsaretheUncertain,ifVGSfortwoMOSFETsaredifferent,ThelinearcurrentwithlargeVGSmaybelargerthanthatthesaturatedcurrentwithsmallVGS.Thetransistorwithsmallcurrent(suchas0.1uA)isalwaysinW.I.No,W/Lshouldbeconsidered,smallW/LresultinalargeevenwhenIDSissmall,thusstillinS.I.;ForaparticularW/L,theMOSFETcanmoreenteringintoW.I.whenIDSis

UniqueI-VmodelofMOSFETinAll

1k'WV

1n

WV S

ox IDS<<IS0,说明<<VT,进入弱反型，否则强反型,附近为过度区,统一的端口归一化电流模型,与夹断电压Vp,沟道电位VD或VSf(r {1f(r

VS(D)

VGn

亚阈斜输出

IFIRIS0(ifir

电流相减的物理依据和好处适合各个偏置工作区域,与原独立模型

数学近似

1if(r1if(r

VS(D)

11if1ir1i1lnxSVDS, 1i1

x

Vx1if1V ln[11if1V

1 ln1 1,

VxVSor ln1if1if1iR

ln

VS,

Sd Sd

ln[1xS]ln[1xd

ln VplnxSVDS,

统一模型的应用：跨导gm,输出导纳

11if(rgmS(d

2IF(

2IS0

1if(r1if(r 2IS0

VpVS)]2IS0

nk

2kI 2kI 2IS0ln[1exp(VpVS)]2IS0exp(Vp) i

2ISir

)0

,g -

2VDSISV 强反型线V

T

统一模型的应

1if11if

VpVS)]Vp

if>>1,强反

Vp-

V

V

1ifDS 1ifif<<1,弱反

1ln[1exp(VpVS)]exp(VpVS)1i1iV-V 1111 1]

1] )[1exp(DS 根据exp(-VDS/VT)==1/A的饱和条

VlnVln

1

1](2

1i1i反1i1i

1/AgmS/

Whatto MOSFETStructureisdefinedbyProcessOnlytodesignbothinparameterandstructureParameter:W/L,andW,Application:ConnectionofterminalswithinorbetweenMaindeviceandcircuit静态工作点IDS

VGS

VDS阻抗参

,1/图形参 W/工艺参 k频率参

W

1

SPICEModel,HandCalculation&

Level1~3

k’,VTH,(VA),,n, --模拟电路性能与采用的工艺密切相关,同一工艺也有参数工艺角:N-PMOS(tt,ss,ff,sf, R(typical,slow,

仿真技术很DC直流工作AC交流小信号(频率瞬态、噪声特性匹配失调,仿真精度

ComparisonofMOS&

CurrentControlCurrentSourceLargeoutputcurrentdrivingcapability,greatFastspeedduetoandhighgmandlargecurrent VoltageControlCurrentSource(VCCS)Lowvoltage&lowpowerconsumptionHighintegration(gm

(gm

(gm/IC

(1/ / /

DS Although(gm/I)MOSinW.I.isthesameasthatofBJT,butthecurrentIislimited(cannotbetoolarge),sothatgmforMOSisremainlower,andinhighcurrentthecurrentefficientisseriouslyreduced.

DC:I-Vcharacter,Non-linearBehavior;Determinedtheoperationpoint.AC:smallsignalcharacter,gm,gd,rd,LinearCompletedthelinearForsmallsignal,MOStreatedaslinearwhichisDCpointForlargersignal,MOStreatedasnon-linearnoneedforoperationDigital:Largersignalnon-linear,anykind