We found this circuit that converts a direct voltage into a proportional frequency signal. The circuit is from an Electronics Now from April 1993. The JFET can be of any type.
This version of the circuit is from 2000, using a source of negative voltage that allows to obtain...
This somewhat complex circuit was found in the May 1984 issue of Radio Electronics magazine. The...
This basic circuit is from an old documentation. The relay must be 50 mA maximum and must have a...