This negative bias circuit provides negative voltages from 3.5 to 6.5 V sources. The circuit was found in the April 1995 issue of Electronics Now magazine.
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...