After reading about constant current sources, I defined the four cases shown in the pdf. Current should go up to 250 mA.

Implementing B and C with the attached circuit (and its counterpart) is straightforward, but I am not sure how to proceed for A and D. I cannot have Rsense referred to ground anymore.

How could I go away with no fancy ICs?

Gracias for any help.

 

Here's a high-side current source with differential inputs, using a standard op amp, that may be of interest to you.

 

Here's a high-side current source with differential inputs, using a standard op amp, that may be of interest to you.

Wow. Quick and to the point. Have to find time to see how it works.

High-side, have to retain that name.

Gracias!!

 

Two transistor two terminal topologies.