Solve Thevinin Voltage with Dependent Sources - Thvenin Northon

[erezb84]

Suppose i want to find the Thevinin Voltage equivalent between points a and b,
but there are dependent sources in my circuit that depend on the current between points a and b, how should i work?

Thanks!

 

[gneill]

Suppose i want to find the Thevinin Voltage equivalent between points a and b,
but there are dependent sources in my circuit that depend on the current between points a and b, how should i work?

Thanks!

Put your own fixed current source, I, at a-b and use the usual analysis methods to find the voltage V that this current source must have across it while connected to the circuit. Thevenin resistance will then be V/I. Since you now know the Thevenin resistance, the output voltage V and current I, you can work out the Thevenin voltage that sits "behind" the Thevenin resistance to produce V.

 

[jegues]

Put your own fixed current source, I, at a-b and use the usual analysis methods to find the voltage V that this current source must have across it while connected to the circuit. Thevenin resistance will then be V/I. Since you now know the Thevenin resistance, the output voltage V and current I, you can work out the Thevenin voltage that sits "behind" the Thevenin resistance to produce V.

I can't quite remember, but this approach only works if the circuit consists of only dependent sources. (i.e. not a mix of independent/dependent)

Correct?

 

[gneill]

I can't quite remember, but this approach only works if the circuit consists of only dependent sources. (i.e. not a mix of independent/dependent)

Correct?

I would think that it would work in all cases (superposition theorem), but I am willing to be corrected. Can you give an example where it would not work?

 

[DeeNos]

To solve for Thevinin Voltage with dependent sources, we must first understand that Thevinin's theorem states that any linear circuit can be replaced by an equivalent circuit containing a single voltage source and a single resistor. This means that we can simplify our circuit by replacing all independent sources with their internal resistance and all dependent sources with their equivalent independent sources.

To find the Thevinin Voltage equivalent between points a and b, we can follow these steps:

1. Replace all independent sources with their internal resistance.
2. Replace all dependent sources with their equivalent independent sources, which can be found by solving for the current between points a and b.
3. Once all sources have been replaced, we can find the Thevinin Voltage by using the voltage divider rule. This involves finding the total resistance between points a and b and then calculating the voltage across this resistance using Ohm's Law.
4. The resulting voltage is the Thevinin Voltage equivalent between points a and b.

In summary, to find the Thevinin Voltage with dependent sources, we need to replace all sources with their equivalent sources and then use the voltage divider rule to calculate the Thevinin Voltage. This approach simplifies the circuit and allows us to find the Thevinin Voltage without being affected by the presence of dependent sources.