6.012 Spring 2007 Lecture 26 1Lecture 26Analyzing Complex AmplifiersOutline• Two-port hand analysis•Examples• What’s Next?Announcement: Final Examination Monday, May 21, 9:00 am - 12:00am, Johnson; Open Book, Calculator Required.6.012 Spring 2007 Lecture 26 2Multi-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 transistors-usually current or voltage sources.• Find high impedance nodes to estimate frequency response.6.012 Spring 2007 Lecture 26 3Can now understand more complex circuits?Examples:NMOS CDNMOS CS - PMOS CD6.012 Spring 2007 Lecture 26 4Can now understand more complex circuits?PNP CE PNP CC - PNP CE6.012 Spring 2007 Lecture 26 5BiCMOS Voltage AmplifierQualitative 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 responseQ2BM6BM7BM8M9M7M6XQ2Q4M1M3M5M10100 µA35 kΩ5 VVsVBIASvOUT+−+−R6.012 Spring 2007 Lecture 26 6gm1Vgs11/gm2βo2ro2−I2gm6ro6ro7Vsro1IoutI2+−+−VoutRS+−Vgs1Small Signal Voltage GainCascode+Voltage Buffer• Cascode-CS-CB•Rin−−−>∞Rout=βo2ro2gm6ro6ro7Avo=vout2vs=−gm1βo2ro2gm6ro6ro7()≈voutvs• Voltage buffer CD-CCRin′→∞Av≈1Rout=1gm4+1βo4gm3+ gmb3()6.012 Spring 2007 Lecture 26 7Frequency Responseω3dB=1βo2ro2gm6ro6ro7()⎡ ⎣ ⎢ ⎢ ⎤ ⎦ ⎥ ⎥ 1C(µ2+Cgd6+ Cgd3+ 1− AvCgs3()Cgs3+ Cdb6+ Ccs2⎡ ⎣ ⎢ ⎢ ⎤ ⎦ ⎥ ⎥ Avo=vout2vs=−gm1βo2ro2gm6ro6ro7()≈voutvsXβo2ro2rocCµ2Cgd6Cgd3Cdb6+ Ccs2(1−Av3)Cgs36.012 Spring 2007 Lecture 26 8Bode Plotωunity= Avo*ω3dB=gm1Cµ2+ Cgd6+Cgd3+ 1− AvCgs3()Cgs3+ Cdb6+ Ccs2()ω3dB=1βo2ro2gm6ro6ro7()⎡ ⎣ ⎢ ⎢ ⎤ ⎦ ⎥ ⎥ 1C(µ2+Cgd6+ Cgd3+ 1− AvCgs3()Cgs3+ Cdb6+ Ccs2⎡ ⎣ ⎢ ⎢ ⎤ ⎦ ⎥ ⎥ 1VoutVs≈ gm1βo2ro2ω3dBωlog scaleωunity6.012 Spring 2007 Lecture 26 9Large Signal DC Analysis• AssumeVBE=0.7VVGS=1.5V6.012 Spring 2007 Lecture 26 10Wrap-up of 6.012• 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): fτ↑ and gm↑ as L ↓: however, Avomax↓ as L ↓6.012: Introductory subject to microelectronic devices and circuitsFollow-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
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