This circuit was found in 80's Popular Electronics. Transistors are commonly used. The potentiometer R5 adjusts the gain.
Maxim MAX20056B 6 Channel High Brightness LED Controller Maxim Integrated makes available through...
We found this circuit in American documentation from the 1980s. Transistors can be of general use....
This circuit for car engine spot adjustment was found in an 80's Radio Electronics. The circuit...