This circuit from the 80's makes use of two transconductance operationals of the time. Modern equivalents can be used. The circuit does not need to be powered by a symmetrical source.
This circuit is from an English publication from 1978, but it can be assembled with BC548 for TR2...
This simple voltage regulator with FET was found in American documentation from the 1980s....
This circuit was used to regulate the speed of small DC motors of cassette recorders. However, if the...