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OPERATIONAL

AMPLIFIER(PHE-10)

ANKITA SHARMA

BE 4TH SEM EC

SHREE BALAJI INSTITUTE OF

TECNOLOGY &MENEGMENT

+

-

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WHAT IS INSIDE AN

OP AMP?

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Phases of output signal wrt input

input

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Common Emitter Amplifier

Rb

RL

Input

signal

Invertedoutput

signal

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Two matched transistors form a

differential amplifier

input

0 V

-VEE+0.7VConstant

current

= I1+I2

I1 I2

VC1=VCC-I1R2 VC2=VCC-I2R4

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Transisterized

Differential Amplifier

Double ended

input - double

ended output

diff. amp:

vout=A (v1-v2)v1 v2

vout- +

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Transistorized

Differential Amplifier

Differential

Mode signal

Common Mode

signal

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N

o

n

Inverting

input

Single Ended Differential Amplifier

(commonly used in op-amps)

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Op Amp stages with pin-outs of IC741

2

4

7

6

3

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Op amp Comparator Open loop gain of op amp is defined as:

AOL = Vo / VDwhere VD = VNI VINV

Open loop gain of op amp is very high(ideally infinite).

Any small difference between VNI and VINVresults into saturation of output voltage VSATi.e. forVNI< VINVoutput is VSAT and

forVNI> VINV output is + VSAT Value ofVSATis limited by the supply voltage

of op amp

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Important features of Op Amp

1. High open loop gain (ideally infinite)

which implies that even the smallest

difference between the two inputs

results into saturated output voltage

2. High input impedance (ideally infinite)

implies that there is no currentflowing into the input of an op amp

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Op amp Applications

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Inverting Amplifier

Multiplier/Divider circuit, whose gain is decided

by the values of resistors

RfRin

VinVout

+

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Inverting Amplifier Analysis

Iin RfRin

Vin

Vout

If

+

Due to virtual ground:

Iin=Vin / Rin= If= ( Vout/ Rf)

@Vout= (Rf/ Rin )Vin

Rf> Rin multiplier Rf< Rin divider

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Op amp integrator

Vin VoutRin CfVout= (1 / Rin Cf)Vin

dt

Iin If

Iin= Vin / Ri n= If= Cf( dVout/ dt)

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Op amp Differentiator

Vin

Vout

Cin Rf

Vout= RfCin (dVin / dt)

If

Iin

Iin= CindVin /dt = If= Vout/ Rf

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Summary

Op amp can be used for various(mathematical) operations like addition,subtraction, multiplication, division,

differentiation, integration etc. Infinite open loop gain and infinite input

resistance give rise to VIRTUAL GROUND

Op amp is available in a simple to use IC

form which require dual supply Many other applications can be

implemented using op amp

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Thank you !Any Quation .?