This simple power supply circuit triggers when the light on the LDR reaches the level set on the potentiometer. The circuit is from an Electronics Now from July 1995.
We found this circuit in a documentation from the 90's. Information on the A/D converter was not...
This simple test for general purpose NPN and PNP transistors was found in a 1974 publication....
Found in Linear Technology documentation from the 1980s, this circuit has an accuracy of 0.01%....