It serves as a reference, since today we can have simpler and more compact solutions. This circuit is from an Electronics Experimenter Handbook from 1992. The integrated circuits are from that time.
This basic configuration of voltage regulator using operational amplifier and zener was found in a...
This circuit was obtained in a 90’s Popular Electronics. The frequency depends on C1, a component...
We found this circuit in the 1990 Radio Electronics Special Projects magazine. The circuit has a...