Indicated for powering circuits with operational amplifiers, this source was found in Popular Electronics. The output voltage depends on the transformer used, as well as the current.
This circuit was found in a 1967 translation, but it can be easily assembled, as most components can be...
This 1986 documentation circuit provides 3, 4, 5, 6 V voltages under 350 mA for powering walkmans...
We found this circuit in the semiconductor ON manual using couplers of the time. These components...