How do dependent sources change the analysis of a circuit?

In summary, the conversation is discussing how to approach a circuit problem with a dependent source. The recommended steps are to first find the Thévenin equivalent for the circuit and then connect it in series with the remaining components. The conversation also touches on the importance of correctly identifying the open circuit voltage and the need to account for any dependant sources when finding the Thévenin voltage.
  • #1
siylence
7
0

Homework Statement



theveniandep.png

Homework Equations


v = IR

The Attempt at a Solution



Okay, so up until this point, I was doing okay... but now I'm stuck.

I do not understand how I'm supposed to work with this because until now I have not had a dependent source.

Am I supposed to start by doing a KCL on the loop to the left?

Also, this may sound stupid, but on the resistor that is running in parallel, why is there a +/- Vz symbol? Is it just there to point direction of current flow or am I missing something?
 
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  • #2
Am I supposed to start by doing a KCL on the loop to the left?

Yes.
 
  • #3
This always tripped me up too. You see, there's all this stuff on that top node and you are supposed to find the open circuit voltage? Geez. Why is all that stuff there, how can that not be a factor in the open circuit voltage?

So, your assumption is correct! Since the loop to the left is open, you just imagine that stuff is gone and you are just trying to find the voltage across that one resistor (Vz). Since there is a current source...I think you know what to do.
 
  • #4
1st:
find the Th. equivalent for the 8A-3ohm-2ohm circuit.
2nd:
connect the equivalent in series with 4ohm-5Vz
 
  • #5
You can Ignore everything in the branch from the node to port 'a' because current will not travel somewhere that will trap it. After, you analyze what you have left and see what you need. So you need Vth and Rth. To find Rth, zero out your INDEPENDANT SOURCES, then find the Req. Then Rth will equal Req. To find Vth don't assume it is = Vz. Why? because Vth is measured at the terminal 'a' to 'b'. We said there is no current through the branch from node to 'a' so there is no voltage drop through the 4ohm resistor BUT there is a voltage dependant voltage source so you will have to deal with that to find the Vth
 

1. What is Thevenin's theorem with dependent sources?

Thevenin's theorem with dependent sources is a circuit analysis technique that allows for the simplification of a complex circuit into an equivalent circuit with a single voltage source and a single resistor. This theorem is used to analyze circuits that contain dependent sources, which are sources whose output is dependent on the voltage or current in another part of the circuit.

2. How is Thevenin's theorem with dependent sources different from Thevenin's theorem with independent sources?

Thevenin's theorem with dependent sources is different from Thevenin's theorem with independent sources in that it takes into account the effect of dependent sources on the circuit. In Thevenin's theorem with independent sources, the sources are assumed to be fixed and not affected by the rest of the circuit. However, in Thevenin's theorem with dependent sources, the sources are allowed to vary based on the voltage or current in other parts of the circuit.

3. When is Thevenin's theorem with dependent sources typically used?

Thevenin's theorem with dependent sources is typically used when analyzing complex circuits with dependent sources, such as transistors or operational amplifiers. It allows for the circuit to be simplified into a more manageable form without losing accuracy, making it easier to analyze and understand.

4. What is the formula for calculating Thevenin's equivalent voltage with dependent sources?

The formula for calculating Thevenin's equivalent voltage with dependent sources is VTH = VOC + A*VSC, where VOC is the open-circuit voltage, VSC is the short-circuit voltage, and A is the coefficient of the dependent source. This formula is derived from the ratio of the dependent source to the rest of the circuit.

5. Can Thevenin's theorem with dependent sources be applied to AC circuits?

Yes, Thevenin's theorem with dependent sources can be applied to AC circuits. However, in AC circuits, the equivalent voltage and resistance are represented using complex numbers instead of real numbers, and the dependent sources are also represented using complex numbers. The same formula can be used to calculate the Thevenin equivalent voltage, but with complex numbers instead of real numbers.

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