LectureAid6

LectureAid6 - EE 541 Prof John Choma Professor Class Lecture Week 6 Ming Hsieh Department of Electrical Engineering University of Southern

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EE 541 Class Lecture Week 6 Transconductor Applications Fall 2008 Semester Prof. John Choma, Professor Ming Hsieh Department of Electrical Engineering University of Southern California University Park; MC: 0271; PHE #604 Los Angeles, California 90089-0271 213-740-4692 [USC Office] 213-740-7581 [USC Fax] [email protected]
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University of Southern California EE 541 Fall 2008/Choma 128 Overview Of Lecture Overview Of Lecture z Miscellaneous Applications ± Open Loop Integrator ± Active Tunable Resistance ± Lowpass Tunable Amplifiers ± Gyrator-Based Active Inductors ± Impedance Transformers ± Quadrature Oscillator z Biquadratic Filters ± Filter Examples ² Lowpass ² Highpass ² Bandpass ² Notch ² Delay ± Generalized Architecture
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University of Southern California EE 541 Fall 2008/Choma 129 + V s R s C V o + G m Phase Inverting + V s R s C V o + G m Non-Phase Inverting + + V s R s C V o Active Integrators Active Integrators z Conventional Op-Amp Integrator ± Feedback Demands Op-Amp Pole Dominance ± Band-Limited By Op-Amp Compensation ± Unity Gain Frequency ( ω m ) Dependent On Source Resistance z Transconductor Integrator (OTA-C) ± Open Loop; No Feedback ± Better Frequency Response Than Op-Amp ± Unity Gain Frequency Independent Of Source Resistance z Note 90º Phase Shift In All Integrators om s s V ω 1 Vs R Cs =− omm s VG ω ±± ==
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University of Southern California EE 541 Fall 2008/Choma 130 + V s R s C V o V o + G m Phase Inverting GV mi r o C o C r C C i + V s R s + V i OTA OTA - - C (Integrator) Model C (Integrator) Model z Ideal Integrator ± Infinite Input Impedance ± Infinite Output Impedance ± 90º Relative Phase Shift z Practical Integrator ± Input Capacitance (C i ) ± Output Capacitance (C o ) ± Feedback Capacitance (C r ) ± Output Resistance (r o ) omu s VG ω Vs Cs =− mo r o s 12 s Gr 1 z V V ss 11 p p ⎛⎞ ⎜⎟ ⎝⎠ ++ z Design Objectives ± Negligible C r (Plausible For Multistage) ± Small Source Resistance, R s ± Very Large r o ± Dominant Net Output Capacitance
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University of Southern California EE 541 Fall 2008/Choma 131 OTA OTA - - C Transfer Relationship C Transfer Relationship z Pole Dominance ± Set At Output Port ± Large r o ± Appended Capacitance, C z Error Function V o GV mi r o C o C r C C i + V s R s + V i ( ) oo 12 1 11 1 rC C pp p +≈ + m r r G z C = () s i s i 2 Rr C CC RC p =+ mo r o s s Gr 1 z V H(s) V ss p p ⎛⎞ ⎜⎟ ⎝⎠ == ++ u r u 1 2 ω s 1 sz ω ε (s) s p s sp =− r 1 2 s 1 z ε (s) p s ± m u o G ω = +
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University of Southern California EE 541 Fall 2008/Choma 132 u r u 1 2 ω s 1 sz ω H(s) ε (s) s p s 11 sp ⎛⎞ ⎜⎟ ⎝⎠ =− ++ OTA OTA - - C Error Function C Error Function z Error Function ± Ideally Is Unity For All Frequencies ± Unity Approximation Requires: z Design For Acceptable Integration Characteristics ± Error Magnitude Must Approach Unity Over Desired Passband ± Error Phase Must Approach Zero Over Desired Passband ² Equivalently, Integrator Delay, Which Is Negative Frequency Derivative
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LectureAid6 - EE 541 Prof John Choma Professor Class Lecture Week 6 Ming Hsieh Department of Electrical Engineering University of Southern

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