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.

Photosensitive power circuit (CB25193E)
This circuit can be used in alarms by activating a relay or a current load that depends on the...
LM3900 Non-Inverter Comparator (CB14207E)
The circuit given below was found in the National Semiconductor Linear Applications Handbook. The...
Phototransistor Currente Control (3) (CB14641E)
The current of this circuit is determined by a PNP transistor. The circuit is suggested by Texas...