> Might help a little by ... A resistor from base to ... very low and ill-determined currents ... tempco of the current regulator diodes ... I remember the author's name ... generally good stuff.
Picky picky. This is 1965!! The 2N2222 was so new, no wonder it got mixed for '2907. Sub-ohm resistors in electronics were nearly unknown... "surely" there should be a "K" there? Typos aside, the performance was miles ahead of most 20V 5 ohm outputs on the market in 1965. And the no-trim self-biasing would not have been possible just a few years earlier... Vbe was not consistent in production.
We could also mention complete lack of protection. Hey, kept us techs employed for decades.
When the '2222 series ramped-up, engineers knew they were "better". My father kept a sample-box of beautiful gold-leg 2N2219. The 2N3713/2N3789 parts were very-very new-for-1965 also. I wonder if C. F. Andren worked for a semi factory.... ah, nope, he was at Applied Physics Laboratory, Johns Hopkins, which means he got to see and think about the New Toys before most folks.
Andren, Carl F.; Fadali, Moneim Ahmed; Gott, Vincent L.; Topaz, Stephen R., "The Skin Tunnel Transformer: A New System that Permits Both High Efficiency Transfer of Power and Telemetry of Data Through the Intact Skin," Biomedical Engineering, IEEE Transactions on , vol.BME-15, no.4, pp.278-280, Oct. 1968
Abstract: Artificial organs which are to be chronically implanted require a means of getting power into the body from an external power source with minimum risk of infection and irritation to the skin. The skin tunnel transformer is such a device whereby high level electromagnetic energy can be transmitted through the skin with very low losses and noncritical positioning. Two versions of the transformer are shown and described, and experimental results obtained with dogs are presented. Transmission over 50 watts at better than 95 percent efficiency has been accomplished with no ill effects. The use of the transformer for simultaneous transmission of telemetry data is also discussed.
"a surgical change to the normal external body geometry of the patient."