I have some left over LM13700 Transconductance Amplifiers hanging around in my parts box and I’m wondering what to do with them. Does anyone have any projects they can recommend that are built around them? Doesn’t look like they have enough bandwidth for some video applications but there’s a lot of very bright people here who will definitely have better ideas!
Maybe make an LFO and use it for sine shaping? There are millions of LFO designs out there like this, but the first one that popped up when I googled just now is probably a good starting place: http://musicfromouterspace.com/analogsynth_new/OLDIESBUTGOODIES/LFO/lfo-3.html
It’s MFOS, so it’s a fairly tried and true circuit. Might want to scale/offset the output to get it to 0-1V (LZX), since it’s probably ±2.5 V (or ±5V?), but that’s just one extra opamp stage per output and a single reference voltage I believe.
Other popular uses of OTAs is for filters. I haven’t quite wrapped my head around how to design filters yet, but again, there are lots of LM13700 filters out there. I think the AI Synthesis one is one of those and has a schematic available. But if you want to filter at video rate (ala the LZX Curtain), I’m not sure what that’d entail or if it can be done with this particular OTA… like I said, I haven’t looked too far into filters.