1. Thevenin and Norton Equivalents
Chapter 4-7
Thevenin and Norton
Equivalents

2. Thevenin and Norton Equivalents:: Useful when interested at what is taking
place at a specific pair of terminals

3. Thevenin equivalent circuit : is a voltage source VTh in series with a
resistance RTh . The combination is equivalent to the original circuit
at the terminals of interest
To find the Thevenin voltage compute the open circuit voltage of the original
circuit at the terminals of interest.

4. Example VTh

5. Example RTh

6. The Value? if apply a load across a and b, the voltage across the load, and
current will be the same as in the original circuit.

7. You Do

9. Alternative method for finding the Thevenin resistance for a network that
contains only independent sources:
Deactivate all independent sources
Short circuit Voltage sources
Open circuit Current sources
Find the equivalent resistance looking into the terminals of interest

11. You Do

12. Alternative method for finding the Thevenin resistance for a network that
contains dependent sources:
Deactivate all independent sources
Short circuit Voltage sources
Open circuit Current sources
Leave dependent sources in circuit
Apply a small test voltage (vT), or small test current (iT), at the terminals of
interest
4. Then the Thevenin resistance is the ration of the voltage across the
test source to the current delivered by the test source

13. Why did I choose vT ?

15. What is the Thevenin voltage?

16. What you should know
Know how to find simple Thevenin and Norton equivalents.