This circuit is a basic current source, with the current through RL = Vs/Rsense. With a circuit like this, for purposes of choosing the op-amp properly, what would the gain be? Some opamps are optimized for unity gain, some for gains > 5 or > 10. With a voltage-in, voltage-out circuit it's easy, but what does "gain" mean in this case, which is basically a trans-impedence application? Turns out that it needs an op-amp that can handle unity-gain; one optimized for gains > 5 oscillate like crazy, but I have no idea why.