I'm in need of a replacement for the CA3080 for my VCO that I would like to build. I have come across the LM13600 and was wondering if anyone knew if I could just use half of it and operate it without connecting to the buffer pins (9,10).
It looks pretty similar, provided you don't get too close to the supply rails (the LM13600 typically has a bit less input common mode range, and a bit less typical swing (both near the negative rail), but the guarantees are similar.
Why wouldn't you use the LM13700? It still seems to be in production, unlike the LM13600 (discontinued 1997) and CA3080 (discontinued 2005).
The LM13600 and LM13700 started out life as a practice piece for a new mask designer. They were thinking about second-sourcing the CA3080, and the new 16-pin package made a dual CA3080 an easy exercise (just flip the layout to do the other side). They had a few pins left over, so they added the Darlington buffers and the predistortion diodes.
The key takeaway is that the LM13600 and the LM13700 are both dual CA3080s with a little something extra added, that you don't have to use if you don't want to.