Table Of ContentEE101: Op Amp circuits (Part 1)
M. B. Patil
[email protected]
www.ee.iitb.ac.in/~sequel
DepartmentofElectricalEngineering
IndianInstituteofTechnologyBombay
M.B.Patil,IITBombay
* TheuseofOpAmpsfreestheuserfromcumbersomedetailssuchastransistor
biasingandcouplingcapacitors.
* ThecharacteristicsofanOpAmparenearlyideal→OpAmpcircuitscanbe
expectedtoperformaspertheoreticaldesigninmostcases.
* AmplifiersbuiltwithOpAmpsworkwithDCinputvoltagesaswell→usefulin
sensorapplications(e.g.,temperature,pressure)
* Theusercangenerallycarryoutcircuitdesignwithoutathoroughknowledgeof
theintricatedetails(nextslide)ofanOpAmp. Thismakesthedesignprocess
simple.
* However,asEinsteinhassaid,weshould“makeeverythingassimpleaspossible,
butnotsimpler.”→needtoknowwheretheidealworldends,andtherealone
begins.
Op Amps: introduction
* TheOperationalAmplifier(OpAmp)isaversatilebuildingblockthatcanbe
usedforrealizingseveralelectroniccircuits.
M.B.Patil,IITBombay
* ThecharacteristicsofanOpAmparenearlyideal→OpAmpcircuitscanbe
expectedtoperformaspertheoreticaldesigninmostcases.
* AmplifiersbuiltwithOpAmpsworkwithDCinputvoltagesaswell→usefulin
sensorapplications(e.g.,temperature,pressure)
* Theusercangenerallycarryoutcircuitdesignwithoutathoroughknowledgeof
theintricatedetails(nextslide)ofanOpAmp. Thismakesthedesignprocess
simple.
* However,asEinsteinhassaid,weshould“makeeverythingassimpleaspossible,
butnotsimpler.”→needtoknowwheretheidealworldends,andtherealone
begins.
Op Amps: introduction
* TheOperationalAmplifier(OpAmp)isaversatilebuildingblockthatcanbe
usedforrealizingseveralelectroniccircuits.
* TheuseofOpAmpsfreestheuserfromcumbersomedetailssuchastransistor
biasingandcouplingcapacitors.
M.B.Patil,IITBombay
* AmplifiersbuiltwithOpAmpsworkwithDCinputvoltagesaswell→usefulin
sensorapplications(e.g.,temperature,pressure)
* Theusercangenerallycarryoutcircuitdesignwithoutathoroughknowledgeof
theintricatedetails(nextslide)ofanOpAmp. Thismakesthedesignprocess
simple.
* However,asEinsteinhassaid,weshould“makeeverythingassimpleaspossible,
butnotsimpler.”→needtoknowwheretheidealworldends,andtherealone
begins.
Op Amps: introduction
* TheOperationalAmplifier(OpAmp)isaversatilebuildingblockthatcanbe
usedforrealizingseveralelectroniccircuits.
* TheuseofOpAmpsfreestheuserfromcumbersomedetailssuchastransistor
biasingandcouplingcapacitors.
* ThecharacteristicsofanOpAmparenearlyideal→OpAmpcircuitscanbe
expectedtoperformaspertheoreticaldesigninmostcases.
M.B.Patil,IITBombay
* Theusercangenerallycarryoutcircuitdesignwithoutathoroughknowledgeof
theintricatedetails(nextslide)ofanOpAmp. Thismakesthedesignprocess
simple.
* However,asEinsteinhassaid,weshould“makeeverythingassimpleaspossible,
butnotsimpler.”→needtoknowwheretheidealworldends,andtherealone
begins.
Op Amps: introduction
* TheOperationalAmplifier(OpAmp)isaversatilebuildingblockthatcanbe
usedforrealizingseveralelectroniccircuits.
* TheuseofOpAmpsfreestheuserfromcumbersomedetailssuchastransistor
biasingandcouplingcapacitors.
* ThecharacteristicsofanOpAmparenearlyideal→OpAmpcircuitscanbe
expectedtoperformaspertheoreticaldesigninmostcases.
* AmplifiersbuiltwithOpAmpsworkwithDCinputvoltagesaswell→usefulin
sensorapplications(e.g.,temperature,pressure)
M.B.Patil,IITBombay
* However,asEinsteinhassaid,weshould“makeeverythingassimpleaspossible,
butnotsimpler.”→needtoknowwheretheidealworldends,andtherealone
begins.
Op Amps: introduction
* TheOperationalAmplifier(OpAmp)isaversatilebuildingblockthatcanbe
usedforrealizingseveralelectroniccircuits.
* TheuseofOpAmpsfreestheuserfromcumbersomedetailssuchastransistor
biasingandcouplingcapacitors.
* ThecharacteristicsofanOpAmparenearlyideal→OpAmpcircuitscanbe
expectedtoperformaspertheoreticaldesigninmostcases.
* AmplifiersbuiltwithOpAmpsworkwithDCinputvoltagesaswell→usefulin
sensorapplications(e.g.,temperature,pressure)
* Theusercangenerallycarryoutcircuitdesignwithoutathoroughknowledgeof
theintricatedetails(nextslide)ofanOpAmp. Thismakesthedesignprocess
simple.
M.B.Patil,IITBombay
Op Amps: introduction
* TheOperationalAmplifier(OpAmp)isaversatilebuildingblockthatcanbe
usedforrealizingseveralelectroniccircuits.
* TheuseofOpAmpsfreestheuserfromcumbersomedetailssuchastransistor
biasingandcouplingcapacitors.
* ThecharacteristicsofanOpAmparenearlyideal→OpAmpcircuitscanbe
expectedtoperformaspertheoreticaldesigninmostcases.
* AmplifiersbuiltwithOpAmpsworkwithDCinputvoltagesaswell→usefulin
sensorapplications(e.g.,temperature,pressure)
* Theusercangenerallycarryoutcircuitdesignwithoutathoroughknowledgeof
theintricatedetails(nextslide)ofanOpAmp. Thismakesthedesignprocess
simple.
* However,asEinsteinhassaid,weshould“makeeverythingassimpleaspossible,
butnotsimpler.”→needtoknowwheretheidealworldends,andtherealone
begins.
M.B.Patil,IITBombay
Op Amp 741
Actual circuit
V
CC
Q8 Q13 Q14
Q12 Q9
Q15
R6
Symbol
+ Q1 Q2 − Q19 R7 OUT VCC
R5 CC Q18 Q21
Q3 Q4 R10 OUT
−V
EE
Q20
Q23
Q7
Q16
Q5 Q6 Q17
Q10
Q11 R9 R8 Q22
R4 R1 R3 R2 Q24 −V
EE
offset adjust
M.B.Patil,IITBombay
* Theexternalresistances(∼afewkΩ)aregenerallymuchlargerthanRo and
muchsmallerthanRi →wecanassumeRi →∞,Ro →0withoutsignificantly
affectingtheanalysis.
* VCC and−VEE (∼±5V to±15V)mustbesupplied;anOpAmpwillnotwork
withoutthem!
InOpAmpcircuits,thesupplyvoltagesareoftennotshownexplicitly.
Parameter IdealOpAmp 741
A ∞ 105 (100dB)
* V
Ri ∞ 2MΩ
Ro 0 75Ω
Op Amp: equivalent circuit
VCC Ro
Vi Vo Vi Vo
OUT Ri AVVi AVVi
−V
EE
M.B.Patil,IITBombay
* VCC and−VEE (∼±5V to±15V)mustbesupplied;anOpAmpwillnotwork
withoutthem!
InOpAmpcircuits,thesupplyvoltagesareoftennotshownexplicitly.
Parameter IdealOpAmp 741
A ∞ 105 (100dB)
* V
Ri ∞ 2MΩ
Ro 0 75Ω
Op Amp: equivalent circuit
VCC Ro
Vi Vo Vi Vo
OUT Ri AVVi AVVi
−V
EE
* Theexternalresistances(∼afewkΩ)aregenerallymuchlargerthanRo and
muchsmallerthanRi →wecanassumeRi →∞,Ro →0withoutsignificantly
affectingtheanalysis.
M.B.Patil,IITBombay
Description:M. B. Patil
[email protected]. Department of Electrical Engineering The use
of Op Amps frees the user from cumbersome details such as transistor biasing
and .. (to distinguish it from the “open-loop gain” of the Op Amp which is ∼ 105)
.
