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# Circuits Lecture 9: Thevenin and Norton Theorem (2) - PowerPoint PPT Presentation

Circuits Lecture 9: Thevenin and Norton Theorem (2). 李宏毅 Hung- yi Lee. Review - Thevenin and Norton Theorem. Two Terminal Network. Thevenin Theorem. Norton Theorem. Review - Thevenin and Norton Theorem. Two Terminal Network. Two Terminal Network. =.

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### Circuits Lecture 9: Thevenin and Norton Theorem (2)

Review - Thevenin and Norton Theorem

Two

Terminal

Network

Thevenin

Theorem

Norton

Theorem

Review - Thevenin and Norton Theorem

Two

Terminal

Network

Two

Terminal

Network

=

The same concept is applied on isc.

Review - Thevenin and Norton Theorem

suppress

Two

Terminal

Network

Two

Terminal

Network

Two

Terminal

Network

suppress

suppress

Review - Thevenin and Norton Theorem

Find voc

Find isc

Two

Terminal

Network

Two

Terminal

Network

Is it correct?

• Maximum Power Transfer

• Chapter 3.1

• Application of Thevenin Theorem

Negative Communed Power

= Supplied Power

• ConsumedPower

• Suppied Power

-

+

reference current should flow from “+” to “-”

B

B

A

A

-

+

reference current should flow from “-” to “+”

• Larger power

• i-v curse

Ideal sources can supply unlimited power.

• i-v curse

• Larger power

• Real voltage sources cannot supply unlimited power

Real voltage source =

Ideal voltage source + resistor

i-v characters

for real voltage source

• Real current sources cannot supply unlimited power

Real current source =

Ideal current source || resistor

i-v characters

for real current source

Maximum power transfer

power

Power consumed by Rs

Real source

Power consumed by RL

Rs is fixed, increase RL

Maximum power transfer

Maximum power transfer to (consumed by) a load resistance requires RL = Rs:

(Only 25%)

Power consumed by RL

RL is a variable

Find RL which maximizes PL

When dPL/dRL=0,

PLis maximum

dPL/dRL=0, when Rs=RL

Power-transfer efficiency

Eff=50%

When RL= Rs

When RL= Rs

Audio Amplifier

Signals from

Sound Card

Find a speaker that can gain sufficientpower

Difficult to compute the power

Input audio signal

Audio Amplifier

http://angelfire.com/ab3/mjramp/index.html

Thevenin Theorem

Sound Card + Audio Amplifier

(speaker)

Power consumed by RL

Application of Thevenin

• Which value of R can absorb maximum power? Find the power.

+

-

+

-

+

-

pRis maximum when dpR/dR=0

Application of Thevenin

• Which value of R can absorb maximum power? Find the power.

+

-

+

-

+

-

Have to find voc

Application of Thevenin

• Find voc

+

voc

-

+

-

+

-

+

-

Application of Thevenin

• Use Thevenin Theorem several times

+

-

+

-

+

-

+

-

+

-

+

-

Application of Thevenin

• Use Thevenin Theorem several times

+

-

+

-

+

-

+

-

Application of Thevenin

• Use Thevenin Theorem several times

+

-

+

-

+

-

+

-

+

-

Application of Thevenin

• Use Thevenin Theorem several times

+

-

• What value of RL should be used to obtain the maximum available power?

• 1ST ORDER DIFFERENTIABLE EQUATIONS

• 2nd ORDER DIFFERENTIABLE EQUATIONS