I know this is an old thread but it's one of the top results in looking for an LM723 used as a current source so I'm going to put this here.
I've been working on old Techne TE-8D circulating heaters (repair is cheaper than new) in our lab and I had trouble understanding how the LM723 was being used. Turns out it's the current source for the 2-wire RTD sensor that gos in the bath. Here's the schematic I've come up with from looking at the board... obviously pots are needed to tune this old thing. I'm not saying it's a good circuit by modern standards but it's apparently good enough for lab temperature control in the 80s and 90s.
I've been working on old Techne TE-8D circulating heaters (repair is cheaper than new) in our lab and I had trouble understanding how the LM723 was being used. Turns out it's the current source for the 2-wire RTD sensor that gos in the bath. Here's the schematic I've come up with from looking at the board... obviously pots are needed to tune this old thing. I'm not saying it's a good circuit by modern standards but it's apparently good enough for lab temperature control in the 80s and 90s.
