Published by Philips in 1965 documentation, the sensor for this circuit is a common LDR. The transistors are general-purpose types from the time, only TR3 is a power type according to the load.
This circuit was obtained from a 1977 magazine, but can still be mounted using BC548 for TR1 and...
We found this circuit in a European publication from the 1990s. Transistors are still common types...
The figure shows how to add a Darlington stage to an operational amplifier in order to obtain a...