This circuit was found in a 1977 documentation. It limits the voltage from a source using zener diodes on the rectifier bridge. It is an unusual configuration today.
This amplifier from 100 to 150mW was found in a Japanese documentation from 1967. The circuit uses...
This circuit is from a manual of JFETs and can be implemented with the BF245 and for the bipolar...
This source of some amps for voltages up to 40 V was found in an Italian magazine Elettronica...