I came across this circuit in the “Typical Applications” section of the datasheet for the On Semiconductor version of the TL431 programmable voltage reference. I think you will agree that it’s definitely not “typical”.
That’s some old skool Forrest Mims III out-of-the-box shit right there.
Ken Shirriff has an excellent post on the inner workings of the TL431 including a note with some neat history of the part, (it’s 40 years old!) and Dennis Feucht has a 6 part (1,2,3,4,5,6) opus on the part.