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prady
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Join Date: Dec 2009
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Voltage Source vs. Current Source

03/15/2010 9:01 AM

what is the difference between a voltage and a current source ??????........if a current source is going to be connected to a resistor it will produce a voltage drop corresponding to V=I*R and the vice verse , then why to go for a different source for a system, if both does the same job???? give me an example for current source......

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bhankiii
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#1

Re: VI sources

03/15/2010 9:21 AM

A voltage source generates a fixed voltage independent of the load connected to it. So, in your example, a 5V source will supply 5V across the resistor regardless of the value of the resistor (within the power limits of the voltage source) while the current through the resistor varies with the resistance. A current source is the opposite. A 1mA current source will deliver 1mA through the resistor regardless of the value of the resistor (within limits) while the voltage across the resistor varies with the resistance.

A transistor is an example of a current source. The collector current is equal to beta times the base current.
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PWSlack
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#2

Re: VI sources

03/15/2010 9:22 AM

A current source will provide a constant current for resistances from zero up to the point that the unit can no longer support from its internal voltage limit.

A voltage source will provide a constant voltage for resistances from ∞ down to the point that the unit can no longer support from its internal current limit.

In that respect, they are two different animals.

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bhankiii
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#3
In reply to #2

Re: VI sources

03/15/2010 9:25 AM

animals? Is an electric eel a voltage source or a current source?
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PWSlack
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#4
In reply to #3

Re: VI sources

03/15/2010 9:34 AM

That would be telling.

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Anonymous Poster
#5

Re: VI sources

03/15/2010 9:38 AM

An example of the current source (or rather plural) are transducers

The out put (usually 4-20ma) is dependent only upon the input (eg pressure, temperature etc) and as far as you do not exceed the load, it remains so.

I always love to give the mechanical analogy

Current source is PD Pump - gives out a constant flow, theoritically with no drrop, till its limit is reached. And the voltage pressure at the outlet rises to a value it can not handle anymore.

Voltage source is like constant pressure pumps/ pumps with a pressure controller in-line, and current flow varies depending on the restrictions, the voltage pressure at the terminal remains constant.

Both have their place in the circuit whether electrical or hydraulic.
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prady
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#6

Re: VI sources

03/15/2010 11:14 AM

Thank you guys ........I got it...

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ozzb
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#7

Re: VI sources

03/15/2010 11:23 AM

A river has a source, information has a source, people have a source, it's where the come from or flow from. Voltage does not flow current does.

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saarang
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#8

Re: Voltage Source vs. Current Source

04/01/2010 6:07 AM

So,how would a voltage-controlled current source or a current-controlled voltage source work?

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Anonymous Poster (1); bhankiii (2); ozzb (1); prady (1); PWSlack (2); saarang (1)

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