微电子专业外语.ppt

Basic MOS Device PhysicsvThe first step is to determine the simplest device model that can represent the role of each transistor with reasonable accuracy.v注意：reasonable Design of Analog COMS Integrated CircuitBasic MOS Device PhysicsvNMOS versus PMOS Devices vIn most CMOS technologies,PMOS devices are quite inferior to NMOS transistors.For example,due to the lower mobility of holes,UpCox 0.25UnCox in modern processes,yielding low current drive and transconductance.Design of Analog COMS Integrated CircuitBasic MOS Device PhysicsvMoreover,for given dimensions and bias currents,NMOS transistors exhibit a higher output resistance,providing more ideal current sources and higher gain in amplifiers.Design of Analog COMS Integrated CircuitBasic MOS Device PhysicsvFor these reasons,it is preferred to incorporate NFETs rather than PFETs wherever possible.v注意：incorporate包含;加上;吸收Design of Analog COMS Integrated CircuitBasic MOS Device PhysicsvLong-Channel versus Short-Channel Devices vIn this chapter,we have employed a very simple view of MOSFETs so as to understand the basic principles of their operation.Design of Analog COMS Integrated CircuitSingle-Stage AmplifiersvAmplification is an essential function in most analog(and many digital)circuits.We amplify an analog or digital signal because it may be too small to drive a load.Design of Analog COMS Integrated CircuitSingle-Stage AmplifiersvIn this chapter,we study the low-frequency behavior of single-stage CMOS amplifiers.Analyzing both the large-signal and the small-signal characteristics of each circuit,we develop intuitive techniques and models that prove useful in understanding more complex systems.v注意：intuitive,complex systemsDesign of Analog COMS Integrated Circuitintuitive,complex systemsvintuitivevntu:tv,-tju:-vadj.直觉的；凭直觉获知的；直观的vcomplex systems复杂系统Design of Analog COMS Integrated CircuitSingle-Stage AmplifiersvAn important part of a designers job is to use proper approximations so as to create a simple mental picture of a complicated circuit.v注意：mental picture Design of Analog COMS Integrated Circuitmental picturevmental picture 记忆图像Mental 英 mentlvadj.内心的，精神的，思想的，心理的；智慧的Design of Analog COMS Integrated CircuitSingle-Stage AmplifiersvThe intuition thus gained makes it possible to formulate the behavior of most circuits by inspection rather than by lengthy calculations.v注意：inspection,lengthy Design of Analog COMS Integrated Circuitvinspection,lengthy vinspection英 nspeknvn.检查；检验；视察；检阅vlengthy 英 leki:,le-vadj.长的，漫长的；冗长的；啰唆的Design of Analog COMS Integrated CircuitSingle-Stage AmplifiersvFollowing a brief review of basic concepts,we describe in this chapter four types of amplifiers:common-source and common-gate topologies,source followers,and cascode configurations.v注意：common-source,common-gate,source followers,cascodeDesign of Analog COMS Integrated Circuitvcommon-source,v common-source 共源v common-gate 共栅v source followers 源跟随v cascode共发共基，共源共栅vTopology 英 tpldi n.拓扑Design of Analog COMS Integrated CircuitSingle-Stage AmplifiersvIn each case,we begin with a simple model and gradually add second-order phenomena such as channel-length modulation and body effect.v注意：begin with Design of Analog COMS Integrated CircuitSingle-Stage AmplifiersvBasic Conceptsv The input-output characteristic of an amplifier is generally a nonlinear function(Fig.3.1)that can be approximated by a polynomial over some signal range.v注意：polynomial Design of Analog COMS Integrated Circuitvpolynomialpolynomial英 plinumjl adj.多项式的，多词学名(指由两个以上的词构成的学名)的Design of Analog COMS Integrated CircuitSingle-Stage AmplifiersvThe input and output may be current or voltage quantities.For a sufficiently narrow range of x.Design of Analog COMS Integrated CircuitSingle-Stage Amplifiersvwhere can be considered the operating(bias)paint and the small-signal gain.Design of Analog COMS Integrated CircuitSingle-Stage Amplifiersv(3.2)provides a reasonable approximation,and higher order terms are insignificant.In other words,indicating a linear relationship between the increments at the input and output.Design of Analog COMS Integrated CircuitSingle-Stage AmplifiersvAs x increases in magnitude,higher order terms manifest themselves,leading to nonlinearity and necessitating large-signal analysis.v注意：manifest,leading to,necessitating Design of Analog COMS Integrated Circuitvlead to,necessitating vto 为介词，因此后面应跟doingHard work leads to success.All roads leads to Rome.vnecessitat英 nisesiteit vt.使成为必要Design of Analog COMS Integrated CircuitSingle-Stage AmplifiersvFrom another point of view,if the slope of the characteristic(the incremental gain)varies with the signal level,then the system is nonlinear.Design of Analog COMS Integrated CircuitSingle-Stage Amplifiersv What aspects of the performance of an amplifier are important?In addition to gain and speed,such parameters as power dissipation,supply voltage,linearity,noise,or maximum voltage swings may be important.v注意：dissipation n 消失；浪费；Design of Analog COMS Integrated CircuitSingle-Stage Amplifiersv Furthermore,the input and output impedances determine how the circuit interacts with preceding and subsequent stages.v注意：interact ntrkt相互作用Design of Analog COMS Integrated CircuitSingle-Stage AmplifiersvIn practice,most of these parameters trade with each other,making the design a multi-dimensional optimization problem.v注意：multi-dimensional多维的:多重的 Design of Analog COMS Integrated CircuitSingle-Stage AmplifiersvIllustrated in the“analog design octagon”,such trade-offs present many challenges in the design of high-performance amplifiers,requiring intuition and experience to arrive at an acceptable compromise.v注意：octagon,trade-off,compromiseDesign of Analog COMS Integrated Circuitvoctagon,trade-off,compromisevoctagonv英 ktgn八边形，八角形 vtrade-off交易；权衡 vcompromise vi.折中解决；妥协，退让 Design of Analog COMS Integrated CircuitSingle-Stage AmplifiersvCommon-source stage with resistive loadvBy virtue of its transconductance,a MOSFET converts variations in its gate-source voltage to a small-signal drain current,which can pass through a resistor to generate an output voltage.Design of Analog COMS Integrated CircuitSingle-Stage AmplifiersvWe study both the large-signal and the small-signal behavior of the circuit.Note that the input impedance of the circuit is very high at low frequencies.Design of Analog COMS Integrated CircuitSingle-Stage AmplifiersvAnalysisv(1):If the input voltage increases from zero,M1 is off and Vout=VDD.vAs Vin approaches VTH,M1 begins to turn on,drawing current from RD and lowering Vout.Design of Analog COMS Integrated CircuitSingle-Stage Amplifiersv(2):If VD VG VTH,M1 is in saturation,vwhere channel-length modulation is neglected,and at point A:Vout=Vin1 VTH.Design of Analog COMS Integrated CircuitSingle-Stage AmplifiersvUsing above equation as the input-output characteristic and viewing its slop as the small-signal gain,Design of Analog COMS Integrated CircuitSingle-Stage AmplifiersvSmall-signal model for the saturation regionDesign of Analog COMS Integrated CircuitSingle-Stage Amplifiersv(3):For Vin Vin1,M1 is in the triode region,vIf Vin is high enough to drive M1 into deep triode region,Vout 2(Vin VTH),thenDesign of Analog COMS Integrated CircuitSingle-Stage AmplifiersvEquivalent circuit in deep triode regionDesign of Analog COMS Integrated CircuitSingle-Stage AmplifiersvEven though derived for small-signal operation,the equation predicts certain effects if the circuit senses a large signal swing.Design of Analog COMS Integrated CircuitSingle-Stage AmplifiersvSince gm itself varies with the input signal,the gain of the circuit changes substantially if the signal is large.v注意：substantially本质上Design of Analog COMS Integrated CircuitSingle-Stage AmplifiersvIn other words,if the gain of the circuit varies significantly with the signal swing,then the circuit operates in the large-signal mode.v注意：significantly值得注目地 Design of Analog COMS Integrated Circuit课上作业In electronics,a common-source amplifier is one of three basic single-stage field-effect transistor(FET)amplifier topologies,typically used as a voltage or transconductance amplifier.The easiest way to tell if a FET is common source,common drain,or common gate is to examine where the signal enters and leaves.The remaining terminal is what is known as common.In this example,the signal enters the gate,and exits the drain.The only terminal remaining is the source.This is a common-source FET circuit.The analogous bipolar junction transistor circuit is the common-emitter amplifier.The common-source(CS)amplifier may be viewed as a transconductance amplifier or as a voltage amplifier.As a transconductance amplifier,the input voltage is seen as modulating the current going to the load.As a voltage amplifier,input voltage modulates the amount of current flowing through the FET.