This circuit was found in a Popular Electronics from the 90s. The circuit uses a general purpose JFET. The coils depend on the signal range that must be amplified.
The circuit shown in the figure shuts off a load when the voltage drops below the value determined...
This circuit was found in an American documentation from 1969. It serves to trigger circuits by...
We found this circuit in an American 1980s documentation. Other comparators can be used and the...