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.
This simple optical alarm circuit was found in the 1991 Electronics Experimenter Handbook. The...
This broadband amplifier was found in an Elektor from the 90's. The gain is 10 dB with a noise...
A recreational application of the 4018 is shown in the figure in which we have electronic dice....