This very low frequency circuit was found in a 1964 Electronic Design. Transistors may be modern equivalents. The filter is low pass type.
As part of a larger project, we found this modulation meter in the August 1994 Electronics Now...
This circuit was found in an 80's Electronic Engineering. The circuit uses operatives of the time...
This circuit is an improvement of the previous one, with the use of two transistors produces a...