Found in old documentation, this circuit is tuned to pass signals below 245 Hz with a level of 0.044 dB above 500 Hz.
Found in a 90's EDN this circuit can be used as a shield. The transistor is a general-purpose type and the...
This circuit was found in the November 1992 issue of Radio Electronics magazine. The circuit has...
This circuit was found in an American documentation from 1977. The circuit can be implemented with modern...