lecture 6: equivalent circuits, max power transfer, superposition nilsson & riedel 4.10-4.13...

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Lecture 6: Equivalent Circuits, Max Power Transfer, SuperpositionNilsson & Riedel 4.10-4.13

ENG17 (Sec. 1): Circuits I

Summer 1 2014

July 1, 2014

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Overview

• Thevenin Equivalent• Norton Equivalent• Special Cases• Maximum Power

Transfer• Superposition

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Thevenin Equivalent Circuit

• Independent voltage source in series with resistor

• Provides simplified equivalence to more complex circuit

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Finding Thevenin Equivalent

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Example

Find equivalent w.r.t. a-b. Then, find I.

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Overview

• Thevenin Equivalent• Norton Equivalent• Special Cases• Maximum Power

Transfer• Superposition

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Norton Equivalent Circuit

• Independent current source in parallel with resistor• Provides simplified equivalence to more complex circuit• Relates to Thevenin Equivalent (source transformation)

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Finding Norton Equivalent

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Overview

• Thevenin Equivalent• Norton Equivalent• Special Cases• Maximum Power

Transfer• Superposition

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With Dependent Source

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Alternate Method

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ExampleFind RN and IN

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Overview

• Thevenin Equivalent• Norton Equivalent• Special Cases• Maximum Power

Transfer• Superposition

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Power Transfer

• Two issues:– Efficiency of Power Transfer– Amount of Power Transfer

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Maximum Power Transfer

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Example

• Find value of RL that results in maximum power transfer.

• Use Thevenin Equivalent circuit.

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Example

Find the value of RL for maximum power transfer. Find the maximum power.

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Overview

• Thevenin Equivalent• Norton Equivalent• Special Cases• Maximum Power

Transfer• Superposition

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Superposition

• Applies to linear system• Defined: when linear system is excited by >1

independent energy sources, the total response is the sum of individual responses.

• Clarified– Deactivate 1st source, find response from 2nd

source– Deactivate 2nd source, find response from 1st

source– Add these responses

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In practice

• May not help so much right now…

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w/Dependent Sources

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Example

Use superposition to find vo.

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Overview

• Thevenin Equivalent• Norton Equivalent• Special Cases• Maximum Power

Transfer• Superposition