This circuit was found in a Popular Electronics from the 90s. The transistors are general purpose, and the gain depends on the ratio between R2 and R1.
This filter that can use any operational was found in a French documentation from 1982. The power...
In the figure we present an extremely simple circuit of a voltage source regulated by a zener...
The maximum current of this power supply is 2 A and the output voltage can be set between 6 and 24 V. The...