07-F10_ActiveFilters

07-F10_ActiveFilters - EE 541 Lecture Aid #7 Fall Semester...

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EE 541 Lecture Aid #7 Fall Semester 2010 Introduction To Active Filter Networks Dr. John Choma, Professor Of Electrical Engineering Ming Hsieh Department of Electrical Engineering Powell Hall Of Engineering (PHE) Room #620 University of Southern California University Park; Mail Code: 0271 Los Angeles, California 90089-0271 (213) 740-4692 [Office] johnc@usc.edu [E-Mail] www.jcatsc.com [Course Notes]
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EE 541 Lecture Aid #7 Active Filter Introduction 381 Overview Of Lecture O Operational Transconductor Topologies For Filter Networks ± NMOS Floating Voltage Cell ² Basic Concept ² Circuit Realization ± COMFET Floating Voltage Cell ± COMFET Linear Transconductor ± NMOS Linear Transconductor O Sallen-Key Filter ± Basic Architecture ± Shortfalls ² Potential Instability ² Finite Amplifier Output Resistance ± 4-Pole Butterworth Example O Other Filter Architectures ± Delyiannis-Friend Bandpass Filter ± Miller Integrator ± Å ckerberg-Mossberg Biquadratic Filter
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EE 541 Lecture Aid #7 Active Filter Introduction 382 NMOS Floating Voltage Cell O Requirements ± M1 And M2 Matched ± Substrates Appropriately Back Biased O Analysis O Result ± Linearity Of Differential I/O Relationship With Respect To Differential Input Voltage ± Transconductance Tunable By V x () 22 nn d1 1 2 x hn d2 2 1 x KK WW IV V V V I V V V V 2L ⎛⎞ = −+− = ⎜⎟ ⎝⎠ + V x V 1 M1 I d1 V gs1 + + V x V 2 M2 I d2 V gs2 + V ss Note: V gs1 = V 1 –V 2 + V x V gs2 = V 2 1 + V x ( ) me 1 2 me n x hn II G V V W G2 K V V L −= ≡−
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EE 541 Lecture Aid #7 Active Filter Introduction 383 Floating Voltage Realization O Analysis O Comments ± M3 And M4 Behave As Nominally Constant Floating Voltage Sources ± All Transistors Matched Except For Indicated Gate Aspect Ratios ± Substrates Are Reverse Biased ± Currents ² i d1 , i d2 Are Signal Currents ² I Q Is A Quiescent Current ± Only n Channel Transistors Used In Signal Paths V 1 M1 i I d1 Q + V x + V 2 M2 i + I d2 Q V ss M3 kI i Qd 2 M4 i 1 V x + x k x k (k 1)I + Q (k 1)I + Q + V dd Requirement: kI Q >> |i d1 |, |i d2 | () 2 Q n Qx h n x h n n 2I K kW kI V V V V 2L K W L ⎛⎞ ≈− + ⎜⎟ ⎝⎠ ( ) ( ) ( ) Q Q me 1 2 me n x hn nQ iI i I G V V W G2 K V V L 8K W L I +− + = =− =
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EE 541 Lecture Aid #7 Active Filter Introduction 384 COMFET Floating Voltage Cell O Analysis O Differential Output Current O Comments ± Linear Differential I/O Relationship ± Effective Transconductance, G me , Tunable Via V x ± Wide Tunability Range Owing To V he = V hn + V hp I d1 M1a M1b + V x V 1 I d2 M2a M2b + V x V 2 I d1 I d2 Parametric Review: p n nn n pp p np W W KK K K LL ⎛⎞ ⎜⎟ ⎝⎠ ±± he hn hp VV V = + ( ) 2 ne dg e h e K IV V 2 =− ne nn pp 11 1 K + ± () 22 ne ne d1 1 2 x he d2 2 1 x V V V I V V V V + = + ( ) me 1 2 me ne x he II G V V G2 K V V −=
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EE 541 Lecture Aid #7 Active Filter Introduction 385 I d1 I Q I Q M1a M1b V 1 I d1 M4b M3a I Q V ss V a I d2 M2a M2b V 2 I d2 M3b M4a I Q V b + V dd + V x COMFET Linear Transconductor O Analysis O Results () 2 Q ne Qx h e x h e 1 b 2 a ne 22 ne ne d1 1 a he d2 2 b he 2I K IV
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07-F10_ActiveFilters - EE 541 Lecture Aid #7 Fall Semester...

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