What is the behavior of ideal voltage/current sources in small signal analysis?

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In summary, ideal voltage/current sources are short circuit for voltage source and open circuit for open circuit in small signal analysis because the output voltage is very stiff for a good voltage source, resulting in Z being equal to 0, and the output current is very little for a good current source, resulting in Z being equal to infinity. This can be seen through the equation Z = V/I, where the symbol for infinity in LaTex is \infty.
  • #1
jinyong
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Can someone please explain why ideal voltage/current sources are short circuit for voltage source and open circuit for open circuit in small signal analysis? Any mathematical proof to this?
 
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  • #2
I would think of it in terms of [tex]Z = \frac{dv}{di}[/tex] (although there may be other ways).

For a good voltage source, the output voltage is very stiff (doesn't change much) as the output current changes, so

[tex]Z = \frac{dv}{di} = \frac{0}{di} = 0[/tex]

But for a good current source, you get very little change in the output current over a wide range of output voltages, so

[tex]Z = \frac{dv}{di} = \frac{dv}{0} = infinity[/tex]


EDIT -- okay, I give up. How do you make the little infinity symbol in LaTex? "\inf" didn't work.
 
  • #3
Berkman is correct.

Voltage source can provide infinite amount of current. And a current source can provide an infinite amount of voltage.

Z = V/I

infty
[tex] \infty [/tex]
 
Last edited:
  • #4
waht said:
infty
[tex] \infty [/tex]

Thanks waht! :biggrin:
 

What is an ideal voltage/current source?

An ideal voltage/current source is a theoretical concept used in electrical engineering and physics. It is a source of electrical energy that maintains a constant output voltage or current regardless of the load connected to it.

What are the characteristics of an ideal voltage/current source?

The main characteristics of an ideal voltage/current source include having no internal resistance, providing a constant voltage or current regardless of the load, and being able to supply an infinite amount of power.

Why are ideal voltage/current sources useful?

Ideal voltage/current sources are useful in circuit analysis and design because they simplify complex circuits and allow for easier calculations. They also serve as a reference for real-world voltage/current sources.

Are there any real-world examples of ideal voltage/current sources?

No, ideal voltage/current sources are purely theoretical and do not exist in the real world. However, some devices such as batteries and power supplies can closely approximate ideal sources under certain conditions.

What are the limitations of ideal voltage/current sources?

Ideal voltage/current sources are idealized models and do not take into account real-world factors such as internal resistance, power limitations, and variability in voltage or current output. They also cannot account for fluctuations in the load connected to them.

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