1
ECE201 Linear Circuit Analysis I
Lecture 14.
Topic:
Maximum Power Transfer
1.
Maximum power transfer for a linear resistor
Under what condition is power absorbed by R
L
maximum?
(1)
When R
L
is a linear resistor (i.e.,
)
P
L
=
i
L
2
R
L
=
v
s
R
s
+
R
L
2
R
L
maximum power transfer occurs when
R
L
= R
s
And
P
L,max
=
v
s
2
4R
s
Proof
:
What value of R
L
maximizes P
L
?
dP
L
dR
L
=
v
s
R
s
+
R
L
2
+
R
L
v
s
2
⋅
−
2
R
s
+
R
L
(
)
3
=
v
s
2
R
s
+
R
L
−
2R
L
R
s
+
R
L
(
)
3
=
v
s
2
R
s
−
R
L
R
s
+
R
L
(
)
3
Set
dP
L
dR
L
=
0, then R
L
=
R
s
or R
L
= ∞
R
v
L
i
L
0

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