《电路》课程英文课件（PPT讲稿）Chapter 5 Operational Amplifier

Chapter 5Operational Amplifier

Chapter 5 Operational Amplifier

IntroductionAn op amp is an active circuit element designed toperform mathematical operation of addition, subtractionmultiplication, division, differentiation, and integrationVt07Balance 18No connectionInverting input 2 006OutputNoninverting input 307b v+Inverting input 26OutputNoninverting input3000415v-045BalanceVWOffsetNull(a)(b)A typical op amp: a) pin configuration, b) circuit symbol

Introduction A typical op amp: a) pin configuration, b) circuit symbol An op amp is an active circuit element designed to perform mathematical operation of addition, subtraction, multiplication, division, differentiation, and integration

Terminal Voltage and CurrentsRo+VccV1V1.RA(V2-V1)-VoAOUTVoOPAMPV2V2-VCC上Vd=V2-V1 (differencial input)Vo=AVd-A(V2-V1)A: gain (open-loop voltage gain)

Terminal Voltage and Currents V2 +Vcc -Vcc V1 Vo OPAMP + - A OUT Vo Ro Ri V1 A(V2-V1) V2 Vd=V2-V1 (differencial input) Vo=AVd=A(V2-V1) A: gain (open-loop voltage gain)

Ro1V1RiA(V2-V1)VoV212Actual op amp: Ri(very large); Ro(very small); A(very large)Idealization: Ri=>oo : Ro=>0 ; A=> 00As Vo is limited, we can get from Vo=A(V2-V1) that: V2=V1As Ri=> o0, we can get ii=O, i2=0

Vo Ro Ri V1 A(V2-V1) V2 Actual op amp: Ri(very large); Ro(very small); A(very large) Idealization: Ri=> ; Ro=>0 ; A=>  As Vo is limited, we can get from Vo=A(V2-V1) that: V2=V1 As Ri=> , we can get i1=0, i2=0 i1 i2

Ideal op ampilV1o1) il=0 ,i2=0 ;VoOUDV22) V1=V2OPAMPi2Ideal op amp model+20630Xi2Vc4

Ideal op amp 1) i1=0 , i2=0 ; V2 2) V1=V2 V1 Vo OPAMP + - OUT Ideal op amp model i1 i2

ApplicationsInverting Amplifier2R2OAR1R1VVoVOOR,++V2ViVoo

Applications Inverting Amplifier i f o v R R v 1 = −

ApplicationsNoninverting amplifierizRfR1V1R?+(1 +V2VRVoViOIfRf-0: R1=oo, then=>

Applications Noninverting amplifier i f o v R R v (1 ) 1 = + If Rf=0; R1=, then=>

Applications9++FirstSecondViVo=VistagestageVViO9The voltage follower

The voltage follower V i V o + - + - First stage Second stage Applications

ApplicationsSumming amplifierRRRRRViORsR2R0i2iR2V20aOi3if R=R=R=R十R30V30Vothen V。 = -(vi +V2 +v3)O

Applications Summing amplifier ( )3 3 2 2 1 1 v R R v R R v R R v f f f o = − + + ( ) 1 2 3 1 2 3 then v v v v if R R R R o f = − + + = = =

DifferenceAmplifierRR (1+R / R2)R7RR (1+R,/R)R1a十RR3R3ifV11R2R422VoRtheny1CRO1ifR=RandR,=Rthen V。= V2 -ViNote: be careful while usingnodal analysis, do not set nodalequation at the output terminal

Difference Amplifier 2 1 3 2 3 4 1 a b 1 4 2 2 3 4 1 2 1 2 (1 / ) (1 / ) v R R v R R R R R R vo − + + = 2 1 1 2 3 4 2 1 1 2 4 3 2 1 ( ) then v v v if R R and R R v v R R then v R R R R if o o = − = = = − = Note: be careful while using nodal analysis, do not set nodal equation at the output terminal