ECEN 215, Principles of Electrical EngineeringDr. Mina RahimianLecture# 6 Date: 9/11/13Thevenin Equivalent CircuitThevenin equivalent circuit is a voltage source in series with a resistor which replaces a resistive network.Norton Equivalent CircuitNorton equivalent circuit is a current source in parallel with a resistor which replaces a resistive network.To find Thevenin equivalent circuit:1. Find the Thevevin voltage by calculating the open circuit voltage. 2. Find the Thevevin resistance : a) If the circuit contains no dependent sources, turn off all independent sources (replace the independent current source with an open circuit and replace the independent voltage source with a short circuit). Then combine the resistors. The Theveninn resistance equals the equivalent resistance. b) If the circuit contains dependent sources, turn off all independent sources and apply a test voltage source at the terminals. Then find the resulting current. The Thevevin resistance is the ratio of the test voltage to the resulting current.(Note: The ratio of the open circuit voltage to the short circuit current, can be ued in both cases to find the Thevevin resistance )Ex. Find the Thevenin equivalent circuit.Ex. Find the Thevenin equivalent circuit.Norton Equivalent CircuitNorton equivalent circuit is a current source in parallel with a resistor which replaces a resistive network.To find the Noton equivalent circuit:1. Find the Norton current, IN by calculating the short circuit current. 2. Find the Norton resistance exactly the same way as the Thevevin resistance : a) If the circuit has no dependent sources, turn off all independent sources (open the independent current sources and short circuit the independent voltage sources). Then combine the resistors. The Norton resistance equals the equivalent resistance. b) If the circuit contains dependent and independent sources, turn off all independent sources and apply a test voltage source at the terminals. Then find the resulting current. The Norton resistance is the ratio of the test voltage to the resulting current.(Note: The ratio of the open circuit voltage to the short circuit current, can always be ued in both cases to find the Norton resistance
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