4-20ma circuit

http://focus.ti.com/docs/prod/folders/print/xtr117.html

The XTR products cannot drive 1kohm. Watch your compliance voltage in 4-20mA applications.

Are you sure? I actually didn't look at the datasheet. In any event:

http://www.analog.com/en/prod/0,2877,AD694,00.html

Here is one spec'ed to drive a 250 ohm load and if that's not enough there is an exampl of how to add a current boosting transistor to the output.

XTR117 is rated to 40 V. 40/1K = 40 mA. More than enough compliance voltage at 40V. At 24 V supply, you could get 24 mA (less a little for loss).

Posts 1>4 will give you good products;

But:

Want to rig up a DIY circuit with not a high accuracy-all analog-mind you ?

3 or 4 Transistors+that few resistors+ 24VC battery is all you will need.

Many in CR4 will come up with brilliant solutions!

Please see another discussion. A lot had been discussed there:
http://cr4.globalspec.com/thread/2905/4-to-20-MA-Source-Circuit-Diagram
<4 to 20 ma source circuit diagram>