西交大微電子考研模擬cmos

1、Chapter 9Operational AmplifiersInstitute of Microelectronics, School of Electronics & Information Eng.Xian Jiaotong Univ.Hongyi Wang （王紅義）Design of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 1wanghongyi9.1 Performance ParametersGainSmall-Signal Bandwidth Large-Signal Bandwidth

2、Output SwingLinearity Noise and OffsetSupply RejectionDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 2wanghongyiExample : Determine the gain of op ampsThe circuit is designed for a nominal gain of 10, i.e., 1+R1/R2=10. Determine the minimum value of A1 for a gain error of 1%

3、(1/b=10).VoutA11+ b A1A1 R2=Vin1+AR + R112» æ 1 öæöVout1ç b ÷ç1- b A ÷Vèøè1 øinTo achieve a gain error less than 1% ,we must have A1>1000The gain of open-loop op amp depends on the required precision in its closed-loop application.D

4、esign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 3wanghongyiSmall-Signal Bandwithfu : U-gain Frequencyf3-dB: -3dB FrequencyDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 4wanghongyi9.2One-Stage Op AmpsFig. 9.6 Simple op amp topologiesDesign of Analog CMOS

5、 Integrated Circuits-Ch.9 Operational Amplifier # 5wanghongyiOne-Stage Op Amp in UGain ConfigurationFig. 9.71»gRout ,CLmNDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 6wanghongyiCascode Op AmpsFig. 9.8Cascode op ampsDesign of Analog CMOS Integrated Circuits-Ch.9 Operati

6、onal Amplifier # 7wanghongyiUGain One Stage CascodeFig. 9.9 Cascode op amp with input and output shortedDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 8wanghongyiFolded Cascode Op AmpsFig. 9.11 Folded cascode circuitsDesign of Analog CMOS Integrated Circuits-Ch.9 Operational

7、Amplifier # 9wanghongyiFolded Cascode Stages (cont.)Fig. 9.11 Folded cascode circuitsDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 10wanghongyiFolded Cascode (cont.)Fig. 9.12 Folded cascode op amp topologyDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier #

8、 11wanghongyiFolded Cascode (cont.)Fig. 9.13 Folded cascode op amp with cascode PMOS loads| Av |» gm1(gm 3 + gmb3)ro3 (ro1 | ro5 )| ( gm 7 + gmb 7)ro7ro9 Design of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 12wanghongyiTelescopic vs. Folded Cascode PoleFig. 9.15Effect of devic

9、e capacitance on the nondominant pole in telescopic and folded-cascode op ampsDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 13wanghongyiExample Folded-Cascode Op AmpFig. 9.16 Realization of a folder-cascode op amp(See Example 9.6)Design of Analog CMOS Integrated Circuits-Ch.

10、9 Operational Amplifier # 14wanghongyiExample 9.6Specification: VDD=3V, differential output swing=3V, power dissipation=10mW, voltage gain=2000。110uA+ 500mV-1.5mA+ 400mV-+ 300mV-110uA0.62.1V110uA+ 400mV-+ 300mV-0.75mA1.5mAÆ VGS2+VOD11=1.35V Æ VGS1=0.95V Æ VOD1,2=0.95-0.7=0.25V Æ

11、(W/L)1,2=400.Æ(W/L)5,6=400, (W/L)3,4=313, (W/L)7-10=278Æ gm1,2= 2ID1,2/VOD1,2=0.006A/V, gm3,4= 0.0038 A/V, gm7,8=0.005A/V.For L=0.5 um,ro1,2=ro7-10= 13.3K, ro3,4 =2ro5,6=6.67K. ÆAV=400Æ L5,6 can be increased to 1.25mm. gm1,2 can be increased by widen W1,2.Design of Analog CMOS In

12、tegrated Circuits-Ch.9 Operational Amplifier # 15wanghongyiSingle-Ended Output Cascode Op AmpsFig. 9.18 cascode op amps with single-ended outputDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 16wanghongyiTriple Cascode|Av| app. (gmro)3/2 Limited Output SwingComplex biasingFig.

13、 9.19 Triple-cascode op ampDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 17wanghongyi9.3Two-Stage Op AmpsFig. 9.20Two-stage op ampDesign Approach for Two-Stage Op AmpsDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 18wanghongyiTwo-Stage Op AmpFig. 9.21

14、 Simple implementation of a two-stage op amp.Design of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 19wanghongyiTwo-Stage Op AmpFig. 9.22 Two-stage op amp employing cascoding.= gm1,2(gm3,4 + gmb3,4 )rO3,4 rO1,2 | (gm5,6 + gmb5,6 )rO5,6rO7,8 ´gm9,10 (rO9,10 | rO11,12 )AvDesign of

15、 Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 20wanghongyiSingle-Ended Output Two-Stage Op AmpFig. 9.23 Two-stage op amp with single-ended outputDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 21wanghongyi9.4 Gain Boosting Output Impedance Enhancement With Feed

16、backFig. 9.24 Increasing the output impedance by feedbackRout= A1 gm2 rO 2rO1Design of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 22wanghongyi9.4 Gain Boosting in Cascode StageFig. 9.25 Gain boosting in cascode stage» gm1 (gm 2rO 2 rO1 )(gm3rO3 )AVDesign of Analog CMOS Integra

17、ted Circuits-Ch.9 Operational Amplifier # 23wanghongyiDifferential Gain BoostingFig. 9.26 Boosting the impedance of a differential cascode stageDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 24wanghongyiDifferential Gain Boosting (cont.)The minimum level at the drain of M3 be

18、coming：VOD3+VGS5+VISS2This level would be one threshold voltage higher.Fig. 9.26 Boosting the impedance of a differential cascode stageDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 25wanghongyiDifferential Gain Boosting (cont.)Fig. 9.27 Folded-cascode circuit used as auxilia

19、ry amplifierDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 26wanghongyiExample 9.7 Calculate the output impedanceFig. 9.28Rout» gm3rO3rO1 gm5 gm7 rO 7 (rO9| rO5 ) | (gm11rO11rO13 )Design of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 27wanghongyiDifferen

20、tial Gain Boosting (cont.)Fig. 9.28 Gain boosting applied to both signal path and load devices.Design of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 28wanghongyi9.6Common-Mode FeedbackThe high gain full differential circuit need CMFBVCM=VDD- (ISS/2)RDFig. 9.30 (a) Simple differentia

21、l pair ;(b) circuit with input shorted to outputDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 29wanghongyiCommon-Mode Feedback (cont.)ID3,4>ISS/2ID3,4<ISS/2=> VX,Yincreases =>M3,4 enter to the triode region=> VX,Ydecreases =>M5 enter to the triode regionFig

22、. 9.31 (a) High-gain differential pair with input shorted to output; (b) effect of current mismatchesDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 30wanghongyiHigh Gain Amp MVout=(IP-IN)(RP|RN)Fig. 9.32 Simplified mof high-gain amplifierDesign of Analog CMOS Integrated Circu

23、its-Ch.9 Operational Amplifier # 31wanghongyiCommon-Mode Feedback (cont.)CMFBs 3 operations1. sensing the Vcom;2. comparison with Vref3. returing the error to the amplifiers bias networkFig. 9.34 Conceptual topology for common-mode feedbackDesign of Analog CMOS Integrated Circuits-Ch.9 Operational A

24、mplifier # 32wanghongyiVcom Sensing I:ResistiveIf R1=R2= R>>Rout1,2Vout,CM=(Vout1+Vout2)/2 Disadvantage：large die area.Fig. 9.35 Common-mode feedback with resistive sensingDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 33wanghongyiVcom Sensing II: Source-FollowerFig. 9.

25、36 Common-mode feedback using source followersDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 34wanghongyiVcom Sensing III: Deep Triode FETFig. 9.38 Common- mode sensing using MOSFETsoperating in deep triode region1R= R=Rtoton7on8W (Vm C+ V- 2V)0OXout 2out1THLDesign of Analog

26、CMOS Integrated Circuits-Ch.9 Operational Amplifier # 35wanghongyiCMFB ExampleControl the current sourceFig. 9.39 sensing and controlling output CM levelDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 36wanghongyiAlternative CMFB for Folded CascodeFig. 9.40 Alternative method

27、of controlling output CM levelDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 37wanghongyiSimplified CMFB with Triode DevicesFig. 9.41 CMFB using triode devicesVout,CM sets a(or a current) such thatI5+I6=I9+I102ID1+ V=+ 2VVout1out 2THW- VGS 5Vbmn COX ( L )7,8Design of Analog C

28、MOS Integrated Circuits-Ch.9 Operational Amplifier # 38wanghongyiCMFB Triode Example with Reference (cont.)Fig. 9.44 Modification of CMFB for more accurate definition of output MC levelDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 39wanghongyiCMFB Triode Example with Referen

29、ce (cont.)Fig. 9.45Modification to suppress error due length modulation.to channel-Design of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 40wanghongyiDifferential Pair with CMFB= gm1,2 (rO1,2 | rO3,4AV| RF )Fig. 9.46(a) Differential pair using diode-connected loads(b) resistive CMFBD

30、esign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 41wanghongyi9.7Input Range LimitationsFig. 9.47 U-gain bufferDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 42wanghongyiInput Range Limitations(Cont.)Fig. 9.48 Extension of input CM rangeDesign of Analog CM

31、OS Integrated Circuits-Ch.9 Operational Amplifier # 43wanghongyi9.8Slew RateFig. 9.50 Response of a linear circuit to input step= V 1- exp -t t = RCVtoutinexp -tdVout= VinttdtDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 44wanghongyiSlewing in Op AmpFig. 9.52 Slewing in an o

32、p amp circuitWhen Vin further increases, the slope keeps constantWe call the slope of the ramp the “slew rate”Design of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 45wanghongyiSmall-Signal Operation of Op AmpFig. 9.53 Small-signal operation of a simple op ampTo amplify the signal V0

33、sinw0t with no distortion the lowest slew rate is w0V0 ( BW-3dB=1/ > w0）Design of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 46wanghongyiOp Amp SlewingFig. 9.54 Slewing during low-to-high transitionSlew rate = ISS/CL (unit.V/ms ). As Vout rises, VX approaches Vin, the circuit re

34、turn to the linear operation.Design of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 47wanghongyiOp Amp Slewing (cont.)Fig. 9.55 Slewing during high-to-low transitionDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 48wanghongyiSlewing in Telescopic Op AmpFig. 9.5

35、7 Slewing in telescopic op ampDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 49wanghongyiFolded-Cascode SlewingFig. 9.58 Slewing in folding-cascode op ampDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 50wanghongyiFolded-Cascode (cont.)Fig. 9.58 Slewing

36、 in folding-cascode op ampDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 51wanghongyiSlewing RecoveryFig. 9.59 Long setting due to overdrive recovery after slewingDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 52wanghongyiSlewing Recovery (cont.)Fig. 9.60 Clamp circuit to limit swing at X and YDesign of Analog CMOS Integrated Circuits-Ch.9 Operational Amplifier # 53wanghongyi9.9Power Supply RejectionPSRR » gmN