voltage source/current source?

[ROCKET SCIENTIST]

Ha ha ha, seems like a big discussion is going on here on my question. Well, I'm not gonna quote any previous comments, just wanna say one thing that I thought myself. From the very basic of electrical theories, we know that voltage is the cause for current and current is the effect of voltage. Moreover as we know, no effect happen without its cause, so we can say, NO VOLTAGE, NO CURRENT !!!
That's why now I think no independent current source can ever exist. Because, every time you have to create voltage first to produce current.
But dependent current sources can exist (transistor circuits), in which we get a fairly constant current over a limited range, but also with a driving voltage !!

Thanks everyone for valuable comments.
Regards,
RS.

 

[Ratch]

RS

That's why now I think no independent current source can ever exist. Because, every time you have to create voltage first to produce current.

A independent current source means that no other parameter in the circuit is controlling it. It does not mean that it lacks the voltage to assure a current will emanate from it.

Ratch

 

[ROCKET SCIENTIST]

Ratch

Originally posted by:
A independent current source means that no other parameter in the circuit is controlling it. It does not mean that it lacks the voltage to assure a current will emanate from it.
Yes, I understand what you are trying to say. You are talking about the peripheral devices. But, think about inside of the current source itself. In there, how could you get current without a voltage? I don't understand. And when you will split the source into it's equivalent circuit, I'm pretty sure that, you will get a driving voltage there. Then, that also becomes a part of the total circuit. Now, tell me If I'm wrong. This thing is kind of confusing.

RS

 

[Ratch]

RS,

You are talking about the peripheral devices.

No, I am talking about any independent current source wherever it may be.

But, think about inside of the current source itself. In there, how could you get current without a voltage?

I said before that a current source has to be able to show a voltage in order to send its current into a circuit. Who cares how it does it? All you have to know is that it can theoretically output a infinite voltage if need be to sustain its designated current. Worrying about the inside of a constant current generator is like getting involved in the electrochemistry of a battery, when all you want to do is loop or node analysis.

And when you will split the source into it's equivalent circuit, I'm pretty sure that, you will get a driving voltage there.

Of course, but who cares about that if you are just doing circuit analysis.

Then, that also becomes a part of the total circuit. Now, tell me If I'm wrong. This thing is kind of confusing

True, but you don't have to pay attention to the inner workings of a current generator, if all you are doing is just doing external analysis.

Ratch

 

[ROCKET SCIENTIST]

Ratch,

ha ha ha, okay friend you win. :-D
Yes, when considering about just outer circuit analysis, you are totally right.
You can just take the current from a black box ignoring what's happening inside.
Thanks for explaining.

RS.