[Alex Eisenhut] needed to replace some old TO-3 voltage regulators ... These three pin metal cans were very common, especially the LM340 5V regulator which was, of course, a linear regulator.

[Kevin Darrah] wanted to make a simple 3.3V regulator without using an integrated ... The circuit isn’t going to beat out a cheap linear regulator IC, but for the low component count, it is ...