模拟集成电路的分析与设计：Chapter 3-Single-Stage Amplifiers.ppt

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,Single-Stage Amplifiers,overview,Common-source,Source follower,Common-gate,Cascode configurations,Study low-frequency behavior of single-stage CMOS amplifiers including:,Develop intuitive(,直观的）,techniques and models useful in understanding complex systems.,Use proper approximations so as to create a simple mental picture of a complicated circuit,and makes it possible to formulate the behavior of most circuits by inspection rather than by lengthy calculations.,Single-Stage Amplifiers,Basic concepts,（,1,）,The input-output characteristics of an amplifier is a nonlinear function(Taylor expansion,泰勒展开）,:,For small range of x,above function can be simplified as:,Where,0,can be considered the bias point,（偏置）,and,1,the small-signal gain(,小信号增益）,Single-Stage Amplifiers,Basic concepts,（,2,）,For small signal increment,x,if we have,:,We call this amplifier a linear amplifier,In fact,due to the noise and distortion etc.,the amplifier is usually not exactly a linear amplifier.So we use a concept of“Linearity”to reveal how this amplifier is more close to a linear amplifier.,Single-Stage Amplifiers,Basic concepts,（,3,）,Besides Linearity,there are some other figures needed to be considered when we design an analog integrated circuit.Below is an“analog design octagon(,八边形规则）”,to show the analog design compromise(,折衷）,:,Single-Stage Amplifiers,common-source(,共源）,with resistive load,（,1,）,Small-signal analysis,Large-signal analysis for bias selection;,While small-signal analysis for amplification,Single-Stage Amplifiers,common-source with resistive load,（,2,）,:Large-signal analysis,When 0,V,in,V,TH,:,M,1,is off and V,out,=V,DD,When V,TH,V,in,V,out,+V,TH,M,1,is in triode region:,When V,in,is high enough,M,1,is in linear(deep triode)region:,Single-Stage Amplifiers,common-source with resistive load,（,3,）,:Small-signal analysis,If M,1,is in saturation region,small-signal gain:,The current and transconductance approch for M,1,:,g,m,or R,D,then A,V,Single-Stage Amplifiers,common-source with resistive load,（,4,）,:Large-signal analysis,Since:,g,m,I,D,power,and in practical design,the overdrive voltage V,in,-V,TH,is limited by voltage slew rate(,压摆率）,:,If we keep I,D,and increase R,D,then,:,R,D,V,RD,output swing(,输出摆幅）,There are always trade-off in analog design!,Single-Stage Amplifiers,common-source with resistive load,（,5,）,:Small-signal analysis,More practical,considering channel-length modulation effect:,Using:,And approximation:,We have:,Note:,Back to CS with source degeneration(11),If no load:,Intrinsic gain,Single-Stage Amplifiers,common-source with resistive load,（,6,）,:Small-signal analysis,Small-signal equivalent circuit becomes:,If R,D,1,then,:,Now G,m,is not dependent on g,m,anymore,means wholly linear amplification.,Conclusion:the common-source amplifier with source resistor is more linear,with the cost of degenerated small signal gain!,Single-Stage Amplifiers,common-source with source degeneration(4),If not account the body effect,：,R,outS,=R,s,+1/g,m,without body effect,R,outD,=R,out,/R,D,R,D,If account the body effect:,R,outD,:the resistance seen at the drain,R,outS,:the total resistance in the source path,A,v,can be achieved by,trick(,捷径）,approximately:,R,outS,=(1+,),R,s,+1/g,m,with body effect,Single-Stage Amplifiers,common-source with source degeneration(5),Calculate output resistance without load:,Normally,(g,m,+g,mb,)r,o,1,then,A,V,is degenerated by a factor of 1+(g,m,+g,mb,)R,S,while R,out,is increased by a factor of 1+(g,m,+g,mb,)R,S,Back to CS with SD(10),Back to CG(7),Single-Stage Amplifiers,common-source with source degeneration(6),Lets remember two of above important equations:,and,Back to CS with SD(8),Single-Stage Amplifiers,common-source with source degeneration(7),Add load and use the transfer function(,传输函数）,analysis method:,I,RS,I,RD,I,ro,S,B,D,G,Single-Stage Amplifiers,common-source with source degeneration(8),Using A,V,=V,out,/V,in,then,G,m,and R,out,Single-Stage Amplifiers,common-source with source degeneration(9),Lemma(,定理）,:,Norton equivalent:,Output shorted to measure I,out,Input shorted to measure R,out,Single-Stage Amplifiers,common-source with source degeneration(10),For common-source without source degeneration:,For common-source with source degeneration:,G,m,R,out,Single-Stage Amplifiers,common-source with source degeneration(11),Example 3.6:,Intrinsic gain,I,o,is ideal,means that R,Io,is infinite(R,io,=,),Explain see page 67!,Single-Stage AmplifiersSource follower(,源跟随器）,(1),Also called common-drain,usually as a voltage buffer because of its high input impedance and low output impedance.,Large-signal:,V,out,follows V,in,!,Single-Stage AmplifiersSource follower,(2),Small-signal:,Single-Stage AmplifiersSource follower,(3),Output resistance:,Single-Stage AmplifiersSource follower,(4),Thevenin(,戴维南,)equivalent for source follower:,Intrinsic source follower gain:,Single-Stage AmplifiersSource follower,(5),source follower gain with load:,Single-Stage AmplifiersSource follower,(6),R,out,of diode conncetion,Single-Stage Amplifierscommon-gate(CG,共栅）,(1),Input from source,output from drain,Single-Stage Amplifierscommon-gate(CG,共栅）,(2),Large signal:,off,sat,tri,If in saturation:,The value is same as that of the common-sourse,besides that it is positive!,Single-Stage Amplifierscommon-gate(CG,共栅）,(3),More general case,with source resistor:,Derivation pls.See p78-79,Single-Stage Amplifierscommon-gate(CG,共栅）,(4),Example 3.11(p.79),using thevenin equivalent:,Correction:p.80,eq.3.107,Last item g,m2,should be g,m1,!,Single-Stage Amplifierscommon-gate(CG,共栅）,(5),Example 3.12(p.81),if R,D,is a current source:,Then R,D,=,and,:,Result can be explained by ignoring R,S,shown as Fig.3.47b,Single-Stage Amplifierscommon-gate(CG,共栅）,(6),Input impedance:,Single-Stage Amplifierscommon-gate(CG,共栅）,(7),Output impedance:,Have a look,Single-Stage AmplifiersCascode(,共源共栅）,(1),Cascode(,套筒）,of a CS stage and a CG stage:,Single-Stage AmplifiersCascode(,共源共栅）,(2),Large-signal analysis:,Condition to assure M1 and M2 in saturation:,The smallest output voltage is the sum of two overdrive;the voltage swing is limited:,off,sat,tri,Single-Stage AmplifiersCascode(,共源共栅）,(3),Small-signal analysis without channel length modulation:,Same as that of the common-source stage!,Single-Stage AmplifiersCascode(,共源共栅）,(4),Small-signal analysis with channel length modulation:,Same as that of the common-source with source degeneration!,Single-Stage AmplifiersCascode(,共源共栅）,(5),Small-signal analysis with channel length modulation:,Approximate calculation!,Single-Stage AmplifiersCascode(,共源共栅）,(6),Small-signal analysis with channel length modulation:,Detail calculation!,(a)Thevenin equivalent to(b),use common-gate calculation,refer to eq.3.113(page 81):,If(g,m2,+g,mb2,)r,o2,1,then:,Same as the result of approximate calculation!,Single-Stage AmplifiersCascode(,共源共栅）,(7),Advantages of cascode(1):,Use small device length to get large output impedance!,Single-Stage AmplifiersCascode(,共源共栅）,(8),Advantages of cascode(2):,Shielding the effect of output voltage change,less mismatch effect!,Reduce mismatch between I,D1,and I,D2,by(g,m3,+g,mb3,)r,o3,!,Single-Stage AmplifiersCascode(,共源共栅）,(9),Folded cascode(,折叠式共源共栅）,:,Cascode of a NMOS and PMOS,reduce voltage drop,but increase power!,Detail pls.See page 91 and 92!,Single-Stage Amplifiers,homework,Q3.2(p93),Q3.17(p96),Q3.21(p98),