Question

Is there any existence of current source practically ?

Answer 1

I've seen current loop sensors, current is less vulnerable to noise than then a tension source, so it's used on noisy high frequency enviroments like presure sensors in industrial HVAC systems, where they use for examples compresors, frequency inverters to drive condenser fans and so on

Answer 2

Well, you don't usually just buy a current source off the shelf (like you do a voltage source), but you design it into your circuits

Answer 3

Yes. Lots of test equipment have both voltage sources and current sources that you can program. Current sources are used a ton in integrated circuits as well.

Answer 4

no @nczempin it's not exactly something to buy off the shelf, but current sources are designed and used thats my point a simple voltage regulator with a shun resistance provides a stable current source for simple use

Answer 5

current sources such as CCS (constant current source) have normally high internal impedances such as the "pentode" or MOSFETs