Woah!
That is a badly designed current source to begin with.
Man, I'm sorry LC, this is the first time I tried this and I'm only 17! I don't know if that still merits any sympathy, but its worth a try
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Looking at what Bob Pease did is to use a trilington(three NPN transistors combination) instead of a single 2N3053 to build an ultra high gain transistor switch and reduce the contribution of Ib to a very very low level. Using even a darlington setup or a MOSFET instead of 2N3053 would be much better in your case.
I couldn't find that article on Bob Pease by the way ("trilington" config.), eventhough I don't actually know who he is, until now (and after tapping his name into Google). However, your suggestion makes sense though, because the transistors that I am currently using offer a gain of about 50, but a TIP121 for example will churn out a gain of 1000.
EDIT (05/08/06 11:48 AM):
I tried using a darlington transistor in the circuit and I got similar results, sort of. The current seems to bounce around what I set it (set at 95.5 mA). I saw a drop of 1 mA in the first 10 mins of operation then the current immediately jumped back up to ~95 mA. After 53-60 mins of operation however, I recorded the current at 95.8 mA. This is good, but I really am not fond of the current varying by 1 mA at the very beginning. Would it be wise to go for a higher gain?
LC, I was hoping you could point me to a book or article that includes information regarding good, accurate variable constant current source design(s).
NG, I set up the voltage reference as shown
**broken link removed** and it did work quite well, however the current dropped, but by only 0.5 mA in 40 mins, which is much better than what I had before (a drop of 2 mA in 10 mins). My apologies for the badly drawn half-schematic in Paint!