This circuit was found in a 80s American documentation. The zener diodes determine the points of action of each stage and the transistors can be general purpose types.
In the figure we have the simple way to implement a voltage reference with an operational one. The...
Found in a Popular Electronics from 1992, this circuit has two output voltages given by the...
This circuit allows the testing of integrated circuits of type 741 (operational amplifier) such as...