Thevenin Self-Review
•  What is a Thevenin Equivalent Circuit?
o Draw a generic Thevenin equivalent circuit
o Discuss and write down 3 good uses for a
Thevenin equivalent circuit, or for the
Thevenin theorem
Op Amps
•  How might you find the maximum
power that can be delivered to any
load from any circuit?
EGR 220, Chapter 5
February 18, 2016
o Why is this an important question?
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Overview
741 Op Amp Circuit Diagram
•  Equivalent circuits
o Thevenin equivalent circuit
o Ideal Op Amp circuit
diagram
•  Op Amp circuit analysis
•  Op Amp wiring diagrams
o Lab 4
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•
http://www.uoguelph.ca/~antoon/gadgets/741/741.html
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Op Amp
Equivalent Circuit Diagram
Op Amp
Equivalent Circuit Diagram
Ia
+Vsource (+15V)
+Vsource (+15V)
Iin 1
Iout
Iin 2
–Vsource (– 15V)
Ib
–Vsource (– 15V)
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Op Amp
Equivalent Circuit Diagram
741 Op Amp Circuit Diagram
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•
http://www.uoguelph.ca/~antoon/gadgets/741/741.html
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Op Amp Circuit Analysis
Transistor Analogy
•  The Golden rules apply
to the Op Amp input:
•  3 terminal device
o  2 terminals – power and ground
o  3rd terminal – input
•  Golden rule #1?
o  Input voltage:
•  Golden rule #2?
o  Input current:
•  Also of interest:
•  Iout = ?
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Op Amp Circuit Analysis
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Find voltage gain vo/vs
•  Analyze Op Amp circuits
o  Apply Golden Rules
o  KCL for input stage (often)
o  KVL or V-divider for output
stage (often)
•  Gain
o  Ratio of output:input
•  Feedback
o  Connect output to input
o  “Feed” the output “back”
to the input
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Inverting Amplifier
Non-inverting Amplifier
Find voltage gain, vo/vi
Find voltage gain, vo/vi
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Op Amps Do Math: Difference Amplifier
à find vo and io 14
Lab: 741 Op Amp On A Chip
+15V
-15V
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Circuit Diagram with Wiring Information
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Op Amp Chip Drawing
Lab (sample)
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The Real Thing: Op Amp Chip
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Notice Color Scheme, Layout &
Feedback Resistor Across the OpAmp
Powering and Wiring an Op Amp
+15V
+15V
-15V
-15V
Power Supply: You will use ±25V and +6V connections
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Power Supply Connections
Lab 4 Circuit 1
+Vcc= +15V
To pin ___?
Your Vin
0<Vin<6V
To pin ___?
-Vcc= -15V
To pin __?
Ground outputs
tied together
To pin ___?
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Lab 4 Pre-Lab
Lab 4 Circuit 2
•  This is a LONG lab
•  You must complete the pre-lab and this
week it will be ‘graded’ as correct or
incorrect
o Wiring diagrams
•  Something possible that shows you are thinking
about this
o Gain & output expressions – correct or not
o Sketch of output – correct or not
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Summary
•  Uses for op amps
o Amplifying an electrical signal
o Basic math functions – analog computers
•  Analysis with op amps uses:
o The Golden Rules
o Often use: KCL and/or Voltage-divider
•  Concepts of gain and feedback
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