I am going to make a laser driver. Most of the schematics I see use a lm317 regulator. Would it be fine if I used a 5v regulator that outputs 1.5 amps instead?
The voltage regulator tries to maintain a constant voltage across R1.
Using Ohm's Law you can calculate the current through R1. This is your constant current.
The GND pin is actually a reference pin. The constant voltage regulator tries to maintain a constant voltage between the output pin and this reference pin.
You can offset this reference pin to a voltage different from 0V.
It looks like I have to use a lm317. I just read somewhere that a laser diode's voltage drop will increase as it gets hotter, so I guess I am going to have to use a lm317 to keep the current constant.
The disadvantage of using the 5V regulator as a current source is that it drops 5V across the sense resistor R1 whereas the LM317 only drops 1.2V. The resistor must thus dissipate 5/1.2 = 4.16 times more power for a given current output.