Electronic Devices and Circuit Theory 10th Edition Boylestad Louis Chapter 11 Op AMP Applications

8/14/2019 Electronic Devices and Circuit Theory 10th Edition Boylestad Louis Chapter 11 Op AMP Applications

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Chapter 11

Op-Amp Applications


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OpOp--Amp ApplicationsAmp Applications

ConstantConstant--gain multipliergain multiplier

Voltage summingVoltage summingVoltage bufferVoltage buffer

Controlled sourcesControlled sources

Instrumentation circuitsInstrumentation circuits

Copyright 2009 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458 All rights reserved.

Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky

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ConstantConstant--Gain AmplifierGain Amplifier

Inverting VersionInverting Version




moremore

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ConstantConstant--Gain AmplifierGain Amplifier

Noninverting VersionNoninverting Version




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MultipleMultiple--Stage GainsStage Gains

= AAAA321

The total gain (3-stages) is given by:

or




55

+=

R3

R

R2

R

R

R1A

ff

1

f


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Voltage SummingVoltage Summing

The output is the sum

of individual signals

times the gain:




[Formula 14.3]

++++++++====

332211o

V

R

V

R

V

R

V

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Voltage BufferVoltage Buffer

Any amplifier with no gain or loss is called a unity gainunity gain

amplifieramplifier.

The advantages of using a unity gain amplifier:

Very high input impedance

Very low output impedance




Realistically these circuits

are designed using equal

resistors (R1 = Rf) to avoid

problems with offset

voltages.

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Controlled SourcesControlled Sources

VoltageVoltage--controlled voltage sourcecontrolled voltage source

VoltageVoltage--controlled current sourcecontrolled current sourceCurrentCurrent--controlled voltage sourcecontrolled voltage source

CurrentCurrent--controlled current sourcecontrolled current source




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VoltageVoltage--Controlled Voltage SourceControlled Voltage Source

The output voltage

is the gain times the

input voltage. Whatmakes an op-amp

different from other

amplifiers is its

Noninverting Amplifier VersionNoninverting Amplifier Version




mpe ance

characteristics and

gain calculations

that depend solely

on external

resistors.

moremore

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VoltageVoltage--Controlled Voltage SourceControlled Voltage Source

The output voltage

is the gain times the

input voltage. Whatmakes an op-amp

different from other

amplifiers is its

Inverting Amplifier VersionInverting Amplifier Version




mpe ance

characteristics and

gain calculations

that depend solely

on external

resistors.

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VoltageVoltage--Controlled Current SourceControlled Current Source

The output currentis:

1kV

VI ========




1

R

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CurrentCurrent--Controlled Voltage SourceControlled Voltage Source

This is simply another way

of applying the op-amp

operation. Whether theinput is a current

determined by Vin/R1 or as

I1:




or

in1

f

outV

RV

====

1212

L1outRIV =


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CurrentCurrent--Controlled Current SourceControlled Current Source

This circuit may appear

more complicated than

the others but it is reallythe same thing.




in

in

f

out

21

in

f

out

inin

f

out

R

V

R

V

R||R

V

R

V

VR

R

V

====

====

====

kIR

R1II

R

RR

R

VI

RR

RRVI

R||R

VI

2

1o

2

21

1

ino

21

21ino

21

in

o

====

++++====

++++====

++++====

====

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Instrumentation CircuitsInstrumentation Circuits

Some examples of instrumentation circuits using op-

amps:

Display driver

Instrumentation am lifier




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Display DriverDisplay Driver




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Instrumentation AmplifierInstrumentation Amplifier




For all Rs at the same value (except Rp):

(((( )))) (((( ))))2121P

o VVkVVR

2R1V ====

++++====

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Active FiltersActive Filters

Adding capacitors to op-amp circuits provides external control of the

cutoff frequencies. The op-amp active filter provides controllable

cutoff frequencies and controllable gain.

Low-pass filter

High-pass filter

Bandpass filter




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LowLow--Pass FilterPass FilterFirstFirst--OrderOrder




11

OHCR2

1f ====

1

fv

R

R1A ++++====

The upper cutoff frequency

and voltage gain are givenby:

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LowLow--Pass FilterPass FilterSecondSecond--OrderOrder




The roll-off can be made steeper by adding more RC networks.

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HighHigh--Pass FilterPass Filter




11

OLCR2

1f ====

The cutoff frequency is determined by:

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BandpassBandpass FilterFilter

There are two cutoff

frequencies: upper and

lower. They can becalculated using the same

low-pass cutoff and high-

pass cutoff frequency




ormu as n e

appropriate sections.

2121

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Electronic Devices and Circuit Theory 10th Edition Boylestad Louis Chapter 11 Op AMP Applications