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