This circuit is from a 1990s publication by William Sheets. The circuit consists of a stage whose gain is adjusted according to the signal intensity.
Found in Popular Elecronics, this configuration also appears in this section, but obtained from other...
This circuit was obtained in an old French publication from the 80s. The maximum power of the lamp...
Found in a 1966 American publication, this circuit invert the phase of a low frequency signal. The...