voltage regulator - Transistor (and Zener) between two power rails - Electrical Engineering Stack Exchange
017 PNP BJT Current Source set with Zener Diode - Electronzap
Transistor-Zener Diode Regulator Circuits
Zener Diodes Kit, 1W Axial Leads Through Hole Power Diode Assorted Assortment Box Kit Set (3.3V/3.6V/3.9V/4.3V/4.7V/5.1V/5.6V/6.2V/6.8V/7.5V), Range 1N4728~1N4737,Pack of 200, By Ltvystore: Amazon.com: Industrial & Scientific
Zener diode setting PNP BJT current source circuit with 2N3906 bipolar junction transistor - YouTube
zener diode with PNP regulator mod for battery charger | Page 2 | Boat Design Net