Found in an EDN from the 90s, this circuit has a distortion of only 0.003%. Capacitors and double potentiometer determine the frequency.
This circuit fires by burning the fuse when the input voltage exceeds the value referenced by the zener....
The UAA180 integrated circuit is no longer manufactured, but if the reader finds one in a scrap...
We find this circuit in a Radio Electronics of July 1984. It consists of the traditional version of 1 A...