[sdiy] Learning about current sinks and sources

[Tom Wiltshire]

Hi All,

Can someone recommend a good site where I could learn about current sinks and sources?

I've seen several different designs and derivations. Some are set up as sinks, some as sources, some inverting, some non-inverting, etc etc. It makes it hard to see what's going on.

I'd like to be able to take an op-amp and a transistor (2N3904/2N3906) and design a sink/source for a particular job, so I need to know how to get the component values I need. For example, with a 0-5V input, how do I organise a 4-20mA output? (Just to choose an example which must have been done lots of times). For something more synthy, how about a 0-5V input and a 0-1mA current for the Ibias pin of a LM13700?
Currently I can't answer questions like this myself, and I'd like to know how to.

Thanks,
Tom