The selected circuit was found in GE's 1977 semiconductor manual. 3N84 is a controlled silicon switch and SCRs support equivalents. The transistor can be a BC558, depending on the supply voltage.
Hig stability is the main feature of the 10 V regulator circuit shown in the figure and suggested by...
Suggested by Sprague in the 1980s documentation, this circuit can control three-phase AC motors....
This circuit uses a 709 operational amplifier that is no longer common today. However, the same...