Norton Equivalent Circuit
Norton’s Theorem
Any two-terminal linear network, composed of
voltage sources, current sources, and resistors,
can be replaced by an equivalent two-terminal
network consisting of an independent current
source in parallel with a resistor.
Network of
Sources
and
Resistors
Norton equivalent circuit
.
+
Arbitrary
Network
v
b
IN
IN
isc
RN
.
a
Network of
Sources
and
Resistors
ob
isc
.
IN = isc
b
isc = IN
RN
oa
+
RN = RTh
VTh
IN =
RTh
Arbitrary
Network
v
b
Finding IN and RN (II)
RTh
IN
RN
.
oa
VTh
a
+
.
Finding IN and RN (I)
We can derive the Norton equivalent circuit
from a Thevenin equivalent circuit simply by
making a source transformation
.
i
i a
IN
RN
voc
-
ob
.
a
Network of
Sources
and
Resistors
+
RN =
voc
.
-
voc
IN
b
voc = RNIN
1
Summary
To determine the Thevenin or Norton
equivalent circuits, we need to calculate any
two of the following three:
• voc
• isc
• Req
Example
Determine the Thevenin and Norton equivalent circuits at
terminals a-b of the following circuit. If a load with RL=10 Ω
is connected across terminals, what’s the power delivered
to the load? What is the power if RL=22.5 Ω and RL=50 Ω ?
VTh = voc
IN = isc
RTh = RN =
voc
isc
2