Found in old documentation, this circuit can be implemented even today with the use of a 2N2646 for the unijunction and a TIC106 for the SCR.
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...