This circuit was found in the April 1993 Electronics Now magazine. With it, it is possible to control the gain of an operational circuit with a JFET.
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...