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Learn about the Thevenin and Norton equivalent circuits, combining voltage and current sources, and source transformations that simplify circuits. Discover how to obtain Thevenin circuits with dependent sources and solve for open circuit voltages.
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E E2415 Lecture 03 - Thévenin and Norton Equivalent Circuits
Combining Voltage Sources Voltage sources are added algebraically
Combining Voltage Sources Voltage sources are added algebraically
Combining Voltage Sources Don’t do this. Why is this illogical? Whose fundamental circuit law is violated by this?
Combining Current Sources Current sources are added algebraically
Combining Current Sources Current sources are added algebraically
Combining Current Sources Don’t do this. Why is this illogical? Whose fundamental circuit law is violated by this?
Obtaining Thévenin Circuit with Dependent Sources • Replace all independent voltage sources with short circuits (0 resistance). • Replace all independent current sources with open circuits ( resistance). • Apply a 1.0 amp current source to the terminal pair. • Resulting terminal voltage numerically equal to Thévenin resistance
Another Thévenin Circuit (1/4) Find open circuit voltage Vab:
Another Thévenin Circuit (2/4) Solve mesh equations for I2 Then Vab can be found:
Another Thévenin Circuit (3/4) Inject One Amp: Now get Thévenin Resistance by node voltage solution:
Check on Previous Example (1/2): • VTh = 12 V and RTh = 3 IN = 4 A • We will calculate IN directly. KVL 1: 20 = 15I1 - 10I2 KVL 2: 0 = 10ix + 8ix ix = 0 I1 = I2
Check on Previous Example (2/2): • VTh = 12 V and RTh = 3 IN = 4 A • We will calculate IN directly. KVL 1: 20 = 15I1 - 10I2 KVL 2: 0 = 10ix + 8ix ix = 0 I1 = I2