Hi,
Is it possible to fabricate a device which is both a constant current source as well as a voltage source at the same time?

 

Depends how you define it. A LM317 can do both jobs, but not at the same time.

I have a Velleman power supply you set the power supply voltage and the maximum current spec (which is another way of saying a constant current source).

However, if you want a constant voltage or a constant current you have to pick which mode. They don't coexist in a single wire/circuit. An application, such as that power supply I mentioned, uses constant voltage until you draw too much current, then the constant current mode takes over and regulates the current, while the voltage will assume whatever it has to to have the current required.

 

Since:

E=IR

If E is constant, and I is constant, what do we know about R?

 

Yep, Don has it right, and this is the only way to possibly make this happen....