•ExamplesLecture 26 Analyzing Complex Amplifiers Outline • Two-port hand analysis • Examples • What’s Next? 6.012 Spring 2009 Lecture 26 1•Multi-Stage Amplifier Analysis • Draw circuit such that signal stages and biasing devices can be easily identified. • Identify signal path and establish amplifier parameters. • Determine function of all other Determine function of all other transistors-usually current or voltage sources. • Find high impedance nodes to estimate frequency response. 6.012 Spring 2009 Lecture 26 2Can now understand more complex circuits? Examples: NMOS CD NMOS CS - PMOS CD 6.012 Spring 2009 Lecture 26 3Can now understand more complex circuits? PNP CE PNP CC - PNP CE 6.012 Spring 2009 Lecture 26 4+MMBiCMOS Voltage Amplifier 5 V R 35 kΩ Q4M6B M3 100 µA Q2B M7B M7 M6 X Q2 M5 + − vOUT M1 V s M10M8 M Qualitative View • Identify signal path and establish amplifier parameters • CS-CB-CD-CC - Good voltage amplifier • Determine function of all other transistors-usually current or voltage sources • Find high impedance nodes to estimate frequency response 8 M9 10 VBIAS + − 6.012 Spring 2009 Lecture 26 5vom1o2o2m6o6o7=out2=out gm1V gs1 1/gm2 β o2r o2−I2 gm6ro6ro7 V s r o1 IoutI2 + − + − Vout RS + − V gs1 Small Signal Voltage Gain Cascode+Voltage Buffer • Cascode-CS-CB • Rin − −− > ∞ Rout = ββββo2 ro2 gm6ro6ro7 A = vout2 = −g ββββr g r r( )≈ vout 6.012 Spring 2009 Lecture 26 6 Avo vs −gm1 ββββo2ro2 gm6 ro6ro7( )≈ vs • Voltage buffer CD-CC Rin ′ → ∞ Av ≈ 1 Rout = 1 gm4 + 1 ββββo4 gm3 + gmb3( ) vin3 vin3 vin4 vin4 vout CD − CC rπ4 + βo4(RL ⎢⎢r o ⎢⎢r oc) (gm3 + gmb3) β o4(gm3 + gmb3) 1 RL 1 gm4 1 + + − + − + − + − + −ssFrequency Response A vo = vout 2 v s = −gm1 β o2r o2 gm6 r o6r o7( )≈ vout v s X β o2r o2 r oc Cµ 2 Cgd 6 Cgd 3 Cdb6 + C cs2 (1 − A v3 )C gs 3 ωωωω3dB = 1 ββββo2ro2 gm6ro6ro7( ) 1 C(µµµµ2 +Cgd6 + Cgd3 + 1− AvCgs3( )Cgs3 + Cdb6 + Ccs2 6.012 Spring 2009 Lecture 26 7ωωωω=Bode Plot V out ≈ gm1β o2ro2 V s 1 ω� ω 3dB log scaleωunity 1 ωωωωunity = Avo * ωωωω3dB = gm1 Cµµµµ2 + Cgd6 + Cgd3 + 1 − AvCgs3( )Cgs3 + Cdb6 + Ccs2( ) ωωωω3dB = 1 ββββo2ro2 gm6ro6ro7( ) 1 C(µµµµ2 +Cgd6 + Cgd3 + 1− AvCgs3( )Cgs3 + Cdb6 + Ccs2 6.012 Spring 2009 Lecture 26 8v22.0 V3.8 V Large Signal DC Analysis • AssumeVBE = 0.7V VGS = 1.5V Q2B M6B M7B M7 M6 Q Q4 M3 M5 100 µA 35 kΩ 5 V 2.0 V 2.0 V 3.5 V 3.0 V 2.0 V 1.5 V 4.5 V 3.5 V 3.0 V 3.8 V R 6.012 Spring 2009 Lecture 26 9 Q2B M8 M9 vOUT Q2 M1 M10 v s VBIAS RS 1.5 V 2.8 V 2.3 V + − + −•MICROELECTRONIC CIRCUITSWrap-up of 6.012 6.012: Introductory subject to microelectronic devices and circuits • MICROELECTRONIC DEVICES – Semiconductor physics: electrons/holes and drift/diffusion, carrier concentration controlled by doping or electrostatically – Metal-oxide-semiconductor field-effect transistors (MOSFETs): drift of carriers in inversion layer – Bipolar junction transistors (BJTs): minority carrier diffusion • MICROELECTRONIC CIRCUITS – Digital circuits (mainly CMOS): no static power dissipation; power ↓↓↓↓, delay ↓↓↓↓ & density ↑↑↑↑ as W & L ↓↓↓↓– Analog circuits (BJT and CMOS): fττττ↑↑↑↑ and gm ↑↑↑↑ as L ↓↓↓↓: however, Avomax ↓↓↓↓ as L ↓↓↓↓Follow-on Courses • 6.152J — Microelectronics Processing Technology • 6.720J — Integrated Microelectronic Devices • 6.301 — Solid State Circuits • 6.374 — Analysis and Design of Digital ICs • 6.775 — Design of Analog MOS ICs 6.012 Spring 2009 Lecture 26 10MIT OpenCourseWarehttp://ocw.mit.edu 6.012 Microelectronic Devices and Circuits Spring 2009 For information about citing these materials or our Terms of Use, visit:
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