EE203-SUNYBuffalo-36-Chapter05-04

EE203-SUNYBuffalo-36-Chapter05-04 - SMALL for Big Things...

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Unformatted text preview: SMALL for Big Things University at Buffalo SMALL for Big Things University at Buffalo nanobioSensors & MicroActuators Learning Lab The State University of New York nanobioSensors & MicroActuators Learning Lab The State University of New York EE 203 Circuit Analysis 2 Lecture 36 Chapter 5.7 More More Realistic Model for OP Amp Simplified (Ideal) Model vs. More Realistic Model for the OP Amp We now consider a more realistic model that predicts the performance of an op amp in its linear region of operation. Such Such a model includes three modifications to the ideal op amp (1) a finite input resistance, Ri; (2) a finite open-loop gain, A; and (3) a nonzero output resistance, Ro. Kwang W. Oh, Ph.D., Assistant Professor SMALL (nanobioSensors and MicroActuators Learning Lab) Department of Electrical Engineering University at Buffalo, The State University of New York 215E Bonner Hall, SUNY-Buffalo, Buffalo, NY 14260-1920 Tel: (716) 645-3115 Ext. 1149, Fax: (716) 645-3656 E-mail: kwangoh@buffalo.edu, http://www.SMALL.Buffalo.edu EE 203 Circuit Analysis 2 | Spring 2008 | Prof. Kwang W. Oh | EE@SUNY-Buffalo Lecture 36 | Chapter 5 | 4/4 | 1/9 EE 203 Circuit Analysis 2 | Spring 2008 | Prof. Kwang W. Oh | EE@SUNY-Buffalo SMALL for Big Things University at Buffalo SMALL for Big Things University at Buffalo nanobioSensors & MicroActuators Learning Lab The State University of New York nanobioSensors & MicroActuators Learning Lab The State University of New York Analysis of an Inverting-Amplifier Circuit (set vp = 0) (1) Analysis of an Inverting-Amplifier Circuit (2) if Node a: is + if = in 1 Rs ( is Node b: - if = io vo = in − ip io vo − vn vo − A( v p − vn ) = Rf Ro = = = A 1 1 1 − ) vn + ( + )vo = 0 Ro R f Ro R f EE 203 Circuit Analysis 2 | Spring 2008 | Prof. Kwang W. Oh | EE@SUNY-Buffalo 1 − R1f vn v = Rs s 1 + R f vo 0 1 Ri 1 Rf + 1 Rf + A Ro Lecture 36 | Chapter 5 | 4/4 | 3/9 1 Rs − 1 Rf + 1 Rf + − 1 Ri 1 Rs − R1f 1 1 Ro + R f 1 Ri 1 Rf 1 1 + Ri )( Ro + Rs Rf + )(1 + Ro Rf − A+ 1+ + 1 ( Rs + + Ro Rf + 1 Rf 1 Rf )+ 1 Rf A ( Ro − Ro Rf )+ Rs Ro Ri R f Rs Rf 1 1 + Ri )( Ro + Ro Rf Ro Rf Rs Ri Rs Ri = − A+ − A+ Rs Rf vs 0 1 Rf 1 1 Ro Rs ( Rs + (1 + Ro AR f R v = − f vs 1 Rs 1 Ro Rs Ro s Rs ( +1+ )+( + )+ Rf A ARi ARi A AR f 1 A 1 Rs vs ( − Ro + R f ) −1+ 1 Ro A Ro vo − vn vo − A(0 − vn ) + =0 Ro Rf ( + 1 Rf 1 Rs 1 1 1 1 1 + + ) vn − vo = vs Rs R f Ri Rf Rs − + A Ro vs − vn vo − vn vn − v p = + Rs Rf Ri vn − vs vn − vo vn − 0 + + =0 Rs Rf Ri Lecture 36 | Chapter 5 | 4/4 | 2/9 (A− Ro Rf ) vs = 1 Rf ) 1 Rf vs = )+ 1 Rf A ( Ro − 1 Rf ) − A+ ( Rss + R Rs Rf + Rs Ri )( Ro + Ro − A+ 1+ Rs Rf + Rs Ri + Ro Rf + Rs Ro Rf Rf Ro Rf Ro Rf )+ Rs Rf ( ARo − Ro Ro Rf Ro Rf + Rs Ro Ri R f R R + A R sf − R sf Ro Rf ) vs vs Ro Rf v vs = R R Rs Rs (1 + A + o ) + ( s + 1) + o Rf Ri Ri Rf − A+ R + A R sf EE 203 Circuit Analysis 2 | Spring 2008 | Prof. Kwang W. Oh | EE@SUNY-Buffalo Lecture 36 | Chapter 5 | 4/4 | 4/9 SMALL for Big Things University at Buffalo SMALL for Big Things University at Buffalo nanobioSensors & MicroActuators Learning Lab The State University of New York nanobioSensors & MicroActuators Learning Lab The State University of New York Analysis of an Inverting-Amplifier Circuit (4) Analysis of an Inverting-Amplifier Circuit (3) vs − vn vo − vn vn − v p + = Rs Rf Ri ∞ ∞ 0 Ri A Ro Ro Rf vo = v Rs R R Rs (1 + A + o ) + ( s + 1) + o Rf Ri Ri Rf Ro AR f = v Rs 1 Ro R 1 Rs ( +1+ )+( s + )+ o Rf A ARi ARi A AR f −1+ Rf Rs is vn − vs vn − vo vn − 0 + + =0 Rs Rf Ri − A+ =− if Node Node a: is + if = in Ideal OP Amp ( is + i f = in − vs − 0 vo − 0 + =0 Rs Rf EE 203 Circuit Analysis 2 | Spring 2008 | Prof. Kwang W. Oh | EE@SUNY-Buffalo vo − vn vo − A( v p − vn ) = Rf Ro vo − vn vo − A(0 − vn ) + Ro Rf ∴ vo = − vs Rf Rs vs ( A 1 1 1 − ) vn + ( + Ro R f Ro R f io ip 1 1 1 1 1 + + ) vn − vo = vs Rs R f Ri Rf Rs Node b: - if = io vs − vn vo − vn + = in Rs Rf in =0 )vo = 0 − A+ vo = Ro Rf Rs R R RR R (1 + A + o + o ) + (1 + o )( s + 1) + o Rf Ri RL RL Ri Rf vs Lecture 36 | Chapter 5 | 4/4 | 5/9 EE 203 Circuit Analysis 2 | Spring 2008 | Prof. Kwang W. Oh | EE@SUNY-Buffalo SMALL for Big Things University at Buffalo SMALL for Big Things University at Buffalo nanobioSensors & MicroActuators Learning Lab The State University of New York nanobioSensors & MicroActuators Learning Lab The State University of New York Analysis of a Noninverting-Amplifier Circuit (1) v −v − vn vo − vn + =− g n Rs Rf Ri + Rg vn vn − vo =0 + + Rs Rf Ri + Rg Analysis of a Noninverting-Amplifier Circuit (2) if Node a: is + if = -ip vn − v g Lecture 36 | Chapter 5 | 4/4 | 6/9 in is ip iL io Node b: - if = io+iL − vo − vn vo − A( v p − vn ) vo = + Rf Ro RL vo − vn vo − A( v p − vn ) vo + + =0 Rf Ro RL v g − vn Ri + Rg = vg − v p Rg v p − vn = v g + EE 203 Circuit Analysis 2 | Spring 2008 | Prof. Kwang W. Oh | EE@SUNY-Buffalo → v p = vg + v g − vn Ri + Rg v g − vn Ri + Rg Rg − vn = Rg v g − vn Ri + Rg Ri Lecture 36 | Chapter 5 | 4/4 | 7/9 EE 203 Circuit Analysis 2 | Spring 2008 | Prof. Kwang W. Oh | EE@SUNY-Buffalo Lecture 36 | Chapter 5 | 4/4 | 8/9 SMALL for Big Things University at Buffalo nanobioSensors & MicroActuators Learning Lab The State University of New York Analysis of a Noninverting-Amplifier Circuit (3) Ideal OP Amp Ri A Ro is ∞ ∞ 0 Rs + R f Rs in ip ip = ∴ vo = if vg − v p Rg =0 ∴ v g = v p ( = vn ) vg is + i f = in vo = EE 203 Circuit Analysis 2 | Spring 2008 | Prof. Kwang W. Oh | EE@SUNY-Buffalo Rs + R f Rs vg Lecture 36 | Chapter 5 | 4/4 | 9/9 ...
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This note was uploaded on 10/19/2011 for the course EE 203 taught by Professor Staff during the Spring '08 term at SUNY Buffalo.

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