This actually helped lead us to our current approach. CCFL inverters more or less do what we are looking for http://search.digikey.com/us/en/products/BXA-12553/289-1049-ND/284629
The question then is how to map it out in Multisim. Wikipedia has a diagram...
Yes, it is a ridiculous task, but that is the task. My source cannot be greater than what you would pull from a dc converter or a few batteries, meaning in the 4-12volt range.
For a senior engineering class I need to design a device that, using a 5 volt source I need to deliver a 5mA current with a load that can vary from 500-100K ohms. Using transistors I know one can create a current limiting circuit, but once the resistance gets high enough (not sure how to...