As in Figure 1, this low-side constant-current source draws a load current of 2.5 V divided by the output resistance through the load resistance, provided that you select the output resistance to make the voltage difference between IC1's input
Figure 2. As in Figure 1, this low-side constant-current source draws a load current of 2.5 V divided by the output resistance through the load resistance, provided that you select the output resistance to make the voltage difference between IC1's input