In this interesting circuit from Popular Electronics, the output voltage is the square root of the input voltage. Equivalent operational amplifiers can be tried out.
We found this circuit in a French documentation from the 80's. The components used are still...
The current of this voltage regulator depends on the transistor which can be a TIP31 for 2 or 3 A....
This goniometer for the medium wave range was found in a 1967 documentation. It can be adapted to work...