What's cursed about this? Operational amplifiers were specifically designed to perform mathematical operations. If anything all the other uses today are the cursed ones (especially as comparators).
I was wondering about this as well. Now I would like about the performance of that multiplier and what kind of multiplication to expect from it (4-quadrant?), but the summing, subtraction and integrator circuits are bog-standard and the first present in most analog signal mixing.
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