Thévenin's theorem

Thevenin’s theorem is a popular theorem, used often for analysis of electronic circuits. This theorem states that a linear circuit containing one or more sources and other linear elements can be represented by a voltage source and a resistance. Using this theorem, a model of the circuit can be developed based on its output characteristic.It was discovered in 1883 by French telegraph engineer Léon Charles Thévenin.

Introduction:

Through the use of thevenin theorem , we have the ability to reduce the complex circuit down to a simple series circuit .

The four steps involved are:

1- First Remove the load.

2- Then determine the voltage seen by the load (Vth).

3- Then replace the voltage source with a short.

4- At the end determine the resistance seen by the load (Rth).

1- Remove the load:

2- Determine the voltage seen by the load (Vth):

Since R2 is not connected at one end as it does not carry any current. Hence it cannot have a voltage drop, the voltage is present only across R3

Vth=VR3

Vth=(R3/R3+R1)*Vs

2- Determine the voltage seen by the load (Vth):

3- Replace the voltage source with a short:

4- Determine the resistance seen by the load (Rth):

Find the total resistance from the open terminal side which is called thevinin equivalent resistance (Rth) by removing actual voltage source from the circuit.

Rth=R2+(R1*R3/R1+R3)

Thevenin equivalent circuit:

Conclusion:

• Certain circuits can be simplified by using Thevenin’s Theorem.

• Equivalent Resistance is essential for the calculation of TEC.

• Ohm’s law is useful in this theorem.• A linear network can be transferred into a

voltage source.