Looking for a Current Source

A DAC and a FET or transistor would work. DAC output resolution would accurately control current sourced per input code. Some older DACs can be had in PDIP packages. BJTs can still be had in 3 lead metal/plastic "cans" & FETs are widely available in 3 or 4 terminal D-PAKs.

Soldering small surface mount devices is easier if you use some liquid flux. Flux will allow the solder to flow & stick better to the metal & the chip leads. If you don't use too much solder, you won't have to worry about bridging across the traces either.

This is a very basic & simplistic explanation, but I hope it helps.

I agree with guest - take a DAC combined with an OPAMP and a FET.

If you are looking for schematics, look for HOWLAND CURRENT SOURCE and you find simple applicable proposals.

One simple example is

www.elecdesign.com/articles/index.cfm?AD=articleID=9018.
Regards Uwe

sorry - the above link didn`t work, so try this:

www.elecdesign.com/articles/articleID/9018/9018.htm
Uwe

If planning for PC control use Tristate buffer like 74HCT573 on Printer port

and use R-2R Resistor network to genrate voltage proportionate to input value,

use it as reference for current source made of descreate MOSFET.

Bharat