This circuit with 24 dB per octave attenuation was found in the November 1973 Radio Electronics magazine. The components are for 1 kHz but can be recalculated for other frequencies.
This circuit was found in a 1968 documentation. The circuit generates three rectangular signals...
We found this circuit in an old documentation from the 70s. The circuit can use any varicap and...
Found in American documentation from the 90's, this circuit is very current and can be implemented with...