Sunday, January 13, 2019

electrical resistance - Thevenin equivalent of a circuit


Ok so I can't post the image of my question and my attempt at it,


so I would like to ask, if anyone knows the steps to simplifying a circuit with dependent current sources, independent voltage sources and resistors, into a Thevenin equivalent circuit.


I tried to use Kirchoff's current law, to find voltage at nodes and then using that I calculated the value of the current flow, but I am not able to find out how to find the Thevenin equivalent resistance of the circuit,


which is the very last step I need to take to get the Thevenin equivalent of the circuit I'm trying to simplify.



Answer



Without dependent sources, zeroing all the independent sources leaves a resistor network so that the Thevenin resistance can be calculated directly.


However, dependent sources typically alter the Thevenin resistance so those can't be zeroed.


One technique is to calculate the open circuit voltage and then place a wire across the nodes and calculate the short circuit current. The ratio of the open circuit voltage to the short circuit current gives the Thevenin resistance.


Another technique is to zero the independent sources and then place a test source across the nodes.



For example, if you place a 1A current source across the nodes and calculate the resulting voltage, the Thevenin resistance in Ohms is just the value of the calculated voltage.


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