Lecture 5 Source Transformation Thevenin Equivalent Circuit Norton Equivalent Circuit.
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Transcript of Lecture 5 Source Transformation Thevenin Equivalent Circuit Norton Equivalent Circuit.
![Page 1: Lecture 5 Source Transformation Thevenin Equivalent Circuit Norton Equivalent Circuit.](https://reader033.fdocuments.us/reader033/viewer/2022061515/56649cd65503460f9499d45a/html5/thumbnails/1.jpg)
Lecture 5
Source TransformationThevenin Equivalent CircuitNorton Equivalent Circuit
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Circuit Techinques
• Ohm’s Law • P=VI• KCL, KVL• Voltage/current divider• Series/parallel resistance• Mesh/Nodal Analysis• Source Transformation• Thevenin/Norton Equivalent Circuit• Superposition Principle• Maximum Power Transfer
![Page 3: Lecture 5 Source Transformation Thevenin Equivalent Circuit Norton Equivalent Circuit.](https://reader033.fdocuments.us/reader033/viewer/2022061515/56649cd65503460f9499d45a/html5/thumbnails/3.jpg)
Source Transformation
Show that iS=vS/R for any RL
![Page 4: Lecture 5 Source Transformation Thevenin Equivalent Circuit Norton Equivalent Circuit.](https://reader033.fdocuments.us/reader033/viewer/2022061515/56649cd65503460f9499d45a/html5/thumbnails/4.jpg)
Thevenin Equivalent Circuit
![Page 5: Lecture 5 Source Transformation Thevenin Equivalent Circuit Norton Equivalent Circuit.](https://reader033.fdocuments.us/reader033/viewer/2022061515/56649cd65503460f9499d45a/html5/thumbnails/5.jpg)
Determine the Thevenin Voltage (VTh)
• If RL=∞ (load across a-b is removed), then Vab=VTH
– RTH does not play a role!
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3 Bit Digital to Analog Converter
741 Op-AmpChapter 5
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Sample DAC Waveform
Digital Input
DAC Output
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Applications
• Most modern audio signals are stored in digital form (e.g. MP3 and CDs) and in order to be heard through speakers they must be converted into an analog signal
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Thevenin Equivalent Circuit
![Page 10: Lecture 5 Source Transformation Thevenin Equivalent Circuit Norton Equivalent Circuit.](https://reader033.fdocuments.us/reader033/viewer/2022061515/56649cd65503460f9499d45a/html5/thumbnails/10.jpg)
Determine VTH
![Page 11: Lecture 5 Source Transformation Thevenin Equivalent Circuit Norton Equivalent Circuit.](https://reader033.fdocuments.us/reader033/viewer/2022061515/56649cd65503460f9499d45a/html5/thumbnails/11.jpg)
Methods of Finding RTH
• RTH=VTH/iSC
– If RL=0, the short circuit current from a to b (i.e. iab) should equal to isc=VTh/RTH.
– So RTH=VTh/isc
• If the network contains only independent sources:– Deactivate a voltage source by replacing it with
a short– Deactivate a current source by replacing it with
an open• If the network contains dependent sources– Apply a test source
![Page 12: Lecture 5 Source Transformation Thevenin Equivalent Circuit Norton Equivalent Circuit.](https://reader033.fdocuments.us/reader033/viewer/2022061515/56649cd65503460f9499d45a/html5/thumbnails/12.jpg)
Calculate the Thevenin Resistance
RTH
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If the network contains only independent sources
RTH?
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RTH
![Page 15: Lecture 5 Source Transformation Thevenin Equivalent Circuit Norton Equivalent Circuit.](https://reader033.fdocuments.us/reader033/viewer/2022061515/56649cd65503460f9499d45a/html5/thumbnails/15.jpg)
Methods of Finding RTH
• RTH=VTH/iSC
– If RL=0, the short circuit current from a to b (i.e. iab) should equal to isc=VTh/RTH.
– So RTH=VTh/isc
• If the network contains only independent sources:– Deactivate a voltage source by replacing it with
a short– Deactivate a current source by replacing it with
an open• If the network contains dependent sources– Apply a test source
![Page 16: Lecture 5 Source Transformation Thevenin Equivalent Circuit Norton Equivalent Circuit.](https://reader033.fdocuments.us/reader033/viewer/2022061515/56649cd65503460f9499d45a/html5/thumbnails/16.jpg)
Degenerated Common Emitter Amplifier (from last lecture)
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What if we drive the base with a small signal?
Vin, m=1 mV Vout, m=46 mV
![Page 18: Lecture 5 Source Transformation Thevenin Equivalent Circuit Norton Equivalent Circuit.](https://reader033.fdocuments.us/reader033/viewer/2022061515/56649cd65503460f9499d45a/html5/thumbnails/18.jpg)
Mesh Analysis (Last Lecture)
ne=2 essential nodesbe=3 essential branches
3-(2-1)=2 equations
![Page 19: Lecture 5 Source Transformation Thevenin Equivalent Circuit Norton Equivalent Circuit.](https://reader033.fdocuments.us/reader033/viewer/2022061515/56649cd65503460f9499d45a/html5/thumbnails/19.jpg)
Mesh Analysis (Last Lecture)
1 2
Clockwise around loop 1:+Vin-i1rπ-(i1+i2)RE=0Counter-clockwise around loop 2:i2=gmi1rπ
Vout =-i2RC
Loop 1: clockwiseLoop 2: counter-clockwise
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Mesh Analysis (Details)
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Determine RTH when a Dependent Source is Present
IT
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Methods of Finding RTH
• RTH=VTH/iSC
– If RL=0, the short circuit current from a to b (i.e. iab) should equal to isc=VTh/RTH.
– So RTH=VTh/isc
• If the network contains only independent sources:– Deactivate a voltage source by replacing it with
a short– Deactivate a current source by replacing it with
an open• If the network contains dependent sources– Apply a test source
![Page 23: Lecture 5 Source Transformation Thevenin Equivalent Circuit Norton Equivalent Circuit.](https://reader033.fdocuments.us/reader033/viewer/2022061515/56649cd65503460f9499d45a/html5/thumbnails/23.jpg)
Another Way to Find RTH
isc
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RTH Calculation
• iSC=10V/100 KOhms=0.1 mA
• VTH=10V/2=5V
• RTH=VTH/iSC=5V/0.1 mA=50 KOhms
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Norton Equivalent Circuit
• A Norton Equivalent circuit consists of–Short-Circuit Current–Norton Equivalent Resistance,
which is equal to Thevenin Equivalent Resistance
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Getting A Norton Equivalent Circuit from Thevenin Equivalent Circuit
Norton Equivalent Circuit
Thevenin Equivalent CircuitVTH
RTH
RTHIN=VTH/RTH
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Derivation of Norton Equivalent Circuit
VTH
RTH
RTHIN=VTH/RTH
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Extra Credit Assignment
Derive 4.1-4.3
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More about the Extra Credit Assignment
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Extra Slides on Thevenin
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Determine vab
Show that VTH=vab
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Determine iSC and RTH
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Example 4.10
Determine the Thevenin Equivalent Voltage
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Example 4.10
1. Determine the short circuit current 2. Determine RTH
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Slides on Source Transformation
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RTH
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Application
Determine whether the 6V source is absorbing or delivering the power.
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Step-by-step simplification
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Redundant Resistor (1)
Prove that the left circuit and the right circuit are equivalent for any load resistor.
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Redundant Resistor (2)
Prove that the left circuit and the right circuit are equivalent for any load resistor.
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Example 4.9
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Simplified Circuit