Transcript ME 6405 – Intro to Mechatronics Operational Amplifiers

ME 6405 – Intro to Mechatronics
Operational Amplifiers
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Table of Content
Overview
Theory
Basic circuits
Advantages /
Disadvantes
Applications
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5.
Overview
Theory of an OP-AMP
Basic circuits
Advantages / Disadvantages
Applications
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Overview
Overview
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Definition: A standard analog circuit component with two
inputs, one output and a very high voltage gain.1
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Typically used for amplification, impedance matching and
mathematical operations
Theory
Basic circuits
Advantages /
Disadvantes
Applications
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History of the OP AMP
Overview
Theory
Basic circuits
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Advantages /
Disadvantes
Applications
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Developed in the early 1940s
Before the invention of the transistor made of vaccum
tubes
Became smaller with tranisistors
Today small, inexpensive integrated circuits
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Schematics of an OP AMP
Overview
Circuit Design of an OP AMP
Theory
Basic circuits
Advantages /
Disadvantes
Applications
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Pin assignment of the IC
Overview
Theory
Basic circuits
Pin Configuration
(1) Offset (Typically Not Used)
Advantages /
Disadvantes
Applications
(2) Inverting Input
(3) Non-Inverting Input
(4) Low Supply
(5) Offset (Typically Not Used)
(6) Output
(7) High Supply
(8) Not Connected
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Properties of an OP-AMP
Overview
Theory
Properties of the ideal
OP-AMP
Properties in reality
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Basic circuits
Advantages /
Disadvantes
Applications
Rin is infinite
Rout is zero
Amplification Vout / Vin is infinite
Unlimited bandwidth
Zero output voltage at zero input
difference
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Finite input resistance
Small, but not zero output
resistance
Finite gain / Saturation
Finite bandwidth
1. THE OP AMP WILL TRY TO MAKE THE VOLTAGE
DIFFERENCE BETWEEN THE TWO INPUTS TO ZERO!
2. THE CURRENT INTO THE OP AMP IS ALWAYS ZERO
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Typical Values of an OP AMP
Overview
Theory
Basic circuits
Advantages /
Disadvantes
Applications
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Property
Ideal
Real
Voltage Gain
∞
105 - 109
Input Resistance
Input Current
∞
0A
106 
10-12 – 10-8 A
Output
Resistance
0
100 – 1000 
Bandwidth
∞
Phaseshift at high
frequencies
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Basic circuits
Overview
Theory
Basic circuits
Advantages /
Disadvantes
Applications
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Comparator e.g. temperature sensor
Linear amplifier
Linear inverting amplifier
Impedance matching
Summing Amplifier
Subtractor
Integrator
Differentiator
Schmitt Trigger e.g. two stage comperator
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Nonlinear Usage - Comparator
Overview
Theory
Basic circuits
Advantages /
Disadvantes
Applications
The nonlinear usage always
works without feedback
Example with reference
voltage UN = 0
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Linear Usage
Overview
Theory
Basic circuits
Advantages /
Disadvantes
Applications
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Inverting Amplifier
Overview
Theory
•Input impedance
infinite, therefore
no current in the
OP AMP
Basic circuits
Advantages /
Disadvantes
Applications
•V+ - V- = 0
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Non Inverting Amplifier
Overview
Theory
•Input impedance
infinite, therefore
no current in the
OP AMP
Basic circuits
Advantages /
Disadvantes
Applications
•V+ = V-
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Summing Amplifier
Overview
Theory
•Input impedance
infinite, therefore
no current in the
OP AMP
Basic circuits
Advantages /
Disadvantes
Applications
•V+ - V- = 0
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Impedance matching
Overview
Theory
Basic circuits
Advantages /
Disadvantes
Applications
Vin= Vout
OP AMP tries to make the voltage difference between
the inverting and the non inverting input to zero
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Subtracting Amplifier
Overview
Theory
Basic circuits
Advantages /
Disadvantes
Applications
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Integrator
Overview
•Input impedance
infinite, therefore
no current in the
OP AMP
Theory
Basic circuits
Advantages /
Disadvantes
Applications
•V+ - V- = 0
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Integrator (II)
Overview
Theory
Basic circuits
Integrate
UE
dU A
1
 C
 UA 
U E dt

RE
dt
RC
Advantages /
Disadvantes
Applications
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Differentiator
Overview
Theory
Basic circuits
Make the same calculation as with the integrator,
just switch the resistor and the capacitor
Advantages /
Disadvantes
Applications
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Schmitt Trigger
Overview
Two stage level detector
Theory
Basic circuits
Advantages /
Disadvantes
Applications
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Advantages / Disadvantages
Overview
Theory
Basic circuits
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Advantages /
Disadvantes
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Advantages: cheap, easy to use, effective
Disadvantages: Ideal not possible, phase shift at high
frequencies
Applications: A/D conversion, Filtering, any digital circuit
Applications
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Applications – D/A Converter
Overview
Theory
Basic circuits
Advantages /
Disadvantes
Applications
Picture from Class
Lecture D/A Conversion
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Low Pass
Overview
Theory
Basic circuits
Advantages /
Disadvantes
Applications
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Application - Rectifier
Overview
Theory
The Schmitt Trigger can be used to
rectify a signal in order to get a clock
Basic circuits
Advantages /
Disadvantes
Applications
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Sources
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1 www.siemensauto.com/glossaries/electronics_glossary.html
http://www.ele.uri.edu/Courses/ele343/low.pass/
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Pictures of example circuits taken from
http://www.fh-landshut.de/~wlf/schT/Vorlesung/ST_3.pdf
http://www.elektronik-kompendium.de/sites/bau/0209092.htm
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Some pictures taken from Garcia-Rivera, Newby, Rogge,
Presentation on the 25th of September 2003 in the ME 6405 class
(www.me.gatech.edu/mechatronics_course)
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Questions?
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An output of the Gogia, Sandhu,
Koenig brain factory
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