09-05-2014, 02:52 PM
Thévenin’s and Norton’s Theorems
Overview
In previous chapters, we have seen that it is possible to characterize a circuit consisting of sources
and resistors by the voltage-current (or i-v) characteristic seen at a pair of terminals of the circuit.
When we do this, we have essentially simplified our description of the circuit from a detailed model of
the internal circuit parameters to a simpler model which describes the overall behavior of the circuit as
seen at the terminals of the circuit. This simpler model can then be used to simplify the analysis
and/or design of the overall system.
In this chapter, we will formalize the above result as Thévenin’s and Norton’s theorems. Using these
theorems, we will be able to represent any linear circuit with an equivalent circuit consisting of a single
resistor and a source. Thévenin’s theorem replaces the linear circuit with a voltage source in series
with a resistor, while Norton’s theorem replaces the linear circuit with a current source in parallel with
a resistor.
In this chapter, we will apply Thévenin’s and Norton’s theorems to purely resistive networks.
However, these theorems can be used to represent any circuit made up of linear elements.