I don't understand current sources! Batteries are voltage sources, but how does one actually implement a current source? I was looking at current mirrors to see how they work, and I understand the idea of getting a nearly identical current produced by the other half, but on the diagrams where is the current I_ref coming from? Is that just a voltage source across a resistor? Also, how could I use this to drive a load that was attached to M2's drain?
I appreciate any explanation!