Found in a Westinghouse Silicon Power Handbook from the 60s, this circuit makes use of period components. Special high voltage transistors are used. Zeners are 15 V.
This circuit with power MOSFETs was found in a 1980s Siliconix documentation. Equivalent MOSFETs...
This 80's General Electric circuit is guarded by the noise-guard for operating current. The...
This circuit was obtained in a 1964 Electronic Design. The components used are from that time....