This hybrid audio amplifier from National Semiconductor was found in the June 1994 issue of Electronics Now magazine. It is powered by 24 V.
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...