Thevenin's Theorem

Monday, 20 August 2018

12:46 PM

The load of a circuit is an element that varies in its power usage

Every time the load changes, the circuit would have to be analysed again

 

Thevenin's theorem provides a technique to simplify the analysis by replacing the fixed part of the circuit with an equivalent one known as Thevenin equivalent circuit

 

Thevenin's theorem - A linear two-terminal circuit can be replaced by an equivalent circuit consisting of a voltage source in series with a resistor

 

The voltage source's value is called the Thevenin voltage , and is equal to the open-circuit voltage at the terminals

 

 

Thevenin resistance  is equal to the ratio of the open-circuit voltage to the source-circuit current at the terminal pair.

 

Alternatively,  can be calculated as the input resistance measured at the terminals when all independent sources are turned off (method cannot be used for dependent sources)

 

 

 

It is a powerful technique in circuit analysis with variable loads

It allows us to simplify a large linear circuit

The equivalent circuit behaves externally exactly the same way as the original circuit

The current through the load  (or load current ) and the voltage across the load (load voltage ) is obtained using a simple voltage division, or KVL/KCL