Adjustable reference (CB21540E)

We found this circuit with 5.3V zener in a Philips publication from the 60s. The op amp could be a modern equivalent.

Simple 1 Transistor Shield (CB15480E)
The circuit, shown in the figure, activates a relay when the logic level applied to its input, from...
TDA2870 10 W amplifier (CB10804E)
The traditional circuit was taken from a French magazine Radio Plans that no longer exists but can...
Precision Comparator using Photodiodes (CB4947E)
This circuit makes use of the LM11, 112 or 113 operatives and was found in a 1980s documentation. The...