current and voltage sources

Thread Starter


Joined Sep 29, 2014
Hi All,

I would like to know the difference between a current and a voltage source.
Is it only representation or interpretation that is different?

Thanks in advance ...


Joined Feb 5, 2010
put simply a voltage source will give you a voltage level from which a variable current is available. like a battery.
a current source would provide a specified current and allow voltage to change in ways that will keep that current flowing. like a current limited power supply.


Joined Nov 12, 2008
With a current source the current remains constant and the voltage will change to keep it that way. With a voltage source the voltage remains constant with various currents.


Joined Mar 14, 2008
An ideal voltage source provide a voltage with a zero (apparent) source impedance, i.e. the voltage is independent of the current drawn by the load impedance. Variation of the load impedance causes the current to vary but not the voltage.

An ideal current source provides a current with an infinite (apparent) source impedance, i.e. the current is independent of the voltage across the load impedance. Variation of the load impedance causes the voltage to vary but not the current.

Real sources have limitations, of course, to the amount of voltage and current they can deliver. But with feedback, these ideals can be closely realized within the device's current and voltage limitations.


Joined May 19, 2014
Your question is very very good question. Many devices are much more "understandable" when you view them in the current realm verses the voltage realm. Being able to "think" current as well as voltage is very important.

Here are my descriptions:

A voltage source will vary the current output to keep the voltage constant.
A current source will vary the voltage output to keep the current constant.