This circuit was found in a 80s American documentation. The zener diodes determine the points of action of each stage and the transistors can be general purpose types.
We found this circuit in the Linear Applications Handbook of the National Semiconductor of 1994....
In the figure we have the use of one of the four existing amplifiers in the LM2900 and LM3900 as a...
Based on components from Linear Technology, we find this circuit in a 2005 manual. The circuit...