Nodal Analysis 1 Thevenin and Norton equivalent circuits, Study notes of Law

Download Nodal Analysis 1 Thevenin and Norton equivalent circuits and more Study notes Law in PDF only on Docsity! EE 101: Lect 3 EE Dept., New Mexico Tech Spring 2013 Nodal Analysis 1 1. Select a reference node ... best to choose one side of a voltage source as having zero voltage. 2. Label all the ogher node voltages V1, V2, V3, etc. 3. If any of the nodes have their voltages fixed by a source of emf, label them as Vs1, Vs2, etc. These voltages are not variable, so their values do not have to be calculated. 4. At each node apply Kirchoff’s current law ∑ i = 0. For each equation, express each current in the form (Vx − Vy)/R = 0 where Vx and Vy are the voltages at either end of the resistor R (unless the value of the current is known). 5. The result of the previous step (4) is a set of simultaneous equations which can be solved to obtain the unknown node voltages. 6. For a full analysis, the node voltages can be used to obtain a value for each branch current Thevenin and Norton equivalent circuits 1. Thevenin’s Equivalent circuit (a) Remove the portion of the network across which you want to find the equivalent circuit. (b) Label those two terminals, e.g., A and B. (c) Calculate VTH by finding the open-circuit voltage between the labeled terminals (i.e., VAB = VTH). (d) Calculate Req (by looking at the circuit from the output to the input) by replacing voltage sources with a short circuit and current sources with an open circuit. Req can also be calculated by first determining the short circuit current ISC (this is the current that flows from A to B when these terminals are connected by a short circuit), and calculating Req = VTH/ISC . Draw your circuit as shown below. + −VTH Req A RL B 1From Electronics, second edition, by David Crecraft 1