[SOLVED] Current Source and Voltage Source

[tahir4awan]

In basic electronics we always read voltage as a potential. A force that is responsible for electrons movement what is called current. So it is understood that voltage is nothing but a force which can increase or decrease current to our requirements. Everything in electronics and electrical is electrons dependent i.e they work with electrons movement. Then why we say that this is voltage source and this is current source.

 

[KJ6EAD]

The nomenclature is based on which of the two parameters is fixed within reasonable limits as the load changes. A voltage source will stay at the defined voltage and provide varying current to a varying load while a current source will provide a constant current and deliver a varying voltage to the load as it changes.

That's the somewhat simplified answer since there are voltage and current sources where the named parameter changes in some defined way instead of remaining fixed, but the names still apply to the parameter that is controlled while the other is allowed to vary.

 

[alexan_e]

I think the previous answer is a good explanation of the two types of source.
A voltage or current source imply that the named factor is constant.
You may need some example, a 3w power led which is used very often in the last years, as you can see from the applied graph a small change in the voltage has a fairly large change in the current of the led, you see that a change of about 100-150mv makes the difference between 0.5A and 1A.
If you measure a specific led and set a voltage regulator to the exact voltage for 700mA, then if you try a second sample of the same led you will have a different current higher or lower because of the production tolerance or temperature difference.
Devices like this are best suited for constant current source in which you specify that you want the load to pull 700ma, this constant current source will change the output voltage according to the load so that the current will always be 700ma .
On the other hand consider a reference voltage for an a/d converter, what you need in this case is a very stable voltage so you use a constant voltage source.

Alex