Found in a General Electric documentation from 1970, this circuit is intended to supply a power LED of the time or Solid State Lamp. No information was given about the core used in the transformer.
The operational amplifier taken as an example is uncommon today, but the configuration can be made...
The integrated circuit used in this regulator is not easy to obtain, since the publication is from...
This configuration was obtained in a 1977 FET Databook. The circuit can be practically any JFET...