This circuit was found in a documentation of the 80s, having didactic purpose. For R1 values between 10k to 1M can be used. Transistors are general purpose types.
This circuit was found in a Popular Electronics from the 90s. Transistors are general purpose...
This circuit works with only 1.5 V and can be powered by a solar panel. The circuit is from 1991....
This circuit has a maximum output current of 5 A, and the 2N3055 must have an excellent heat sink....