#### Transcript CSCI 2980: Introduction to Circuits, CAD, and Instrumentation

```EENG 2610: Circuits Analysis
Class 9: Thevenin’s and Norton’s Theorems,
Maximum Power Transfer
Department of Electrical Engineering
College of Engineering, University of North Texas
Example 5.9: Determine Thevenin’s equivalent of the network at terminals A-B.
Circuits containing only dependent sources
V2
EENG 2610, Class 9
V3
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Example 5.10: Determine RTh at terminals A-B.
Circuits containing only dependent sources
V3
EENG 2610, Class 9
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Example 5.11: Use Thevenin’s theorem to find Vo
Circuits containing both independent and dependent sources
EENG 2610, Class 9
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Example 5.12: Use Thevenin’s theorem to find Vo
Circuits containing both independent and dependent sources
EENG 2610, Class 9
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Source Transformation/Source Exchange
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If we have embedded within a network a current source i(t) in parallel with a
resistor R, we can replace this combination with a voltage source of value
v(t) = i(t)R in series with the resistor R.
The reverse is also true; that is, a voltage source v(t) in series with a
resistor R can be replaced with a current source of value i(t) = v(t)/R in
parallel with the resistor R.
Parameters within the circuit are unchanged under these transformations.
We can use source transformations back and forth to simplify circuits.
Important: the two equivalent circuits are equivalent only at the two
external nodes.
RTh
voc
i
A
vo
voc  RTh isc
isc
B
Circuit B
i
RTh
A
vo
B
Circuit B
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Example 5.14: Use source transformation to find Vo
3 k
12 V
2 k
6 k
4 k
2 mA
8 k
VO
EENG 2610, Class 9
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General Rules for Circuit Analysis
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Try to select a simple technique for a given problem,
 First, count the number of nodes and loops.
 Next, examine the type and number of sources.
 Select a technique based on this information, your objective, and
Loop analysis and nodal analysis are straightforward and as
good as any technique that you have learned.
 Equivalency, Linearity, Superposition,
Thevenin’s and Norton’s Theorems
 The real value of these techniques is the insight and
understanding that they provide about the physical nature of the
network.
EENG 2610, Class 9
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Maximum Power Transfer
i
v
R
PL  i 2 RL  (
RL
v
) 2 RL
R  RL
d PL
0
d RL
RL  R
Maximum power transfer takes place
when the load resistance RL  R .
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Thevenin’s theorem provides a way to determine the maximum
power that a circuit can supply; that is, RL  RTh .
EENG 2610, Class 9
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Example 5.16: Find out RL for maximum power transfer and
the maximum power that can be transferred to this load.