This 5-band function generator circuit was found in the April 1994 Electronics Now magazine. The circuit has three possible waveforms and employs additional operationals.
In the figure we have the way to implement a 5 to 45 V zener diode with 50 mA of maximum current...
This circuit is from a Radio Electronics magazine from December 1958. The indicator instrument is analog...
These integrated ones consist of class B amplifiers with gain fixed 24 internally for better...