This circuit was found in the August 1996 Electronics Now magazine. The circuit is based on an operational circuit whose type determines the gains and limits for the frequency.
We found this circuit in the March 1980 Radio Electronics magazine. The circuit used is the HA2400...
This circuit rejects frequencies around 1 kHz and can be adjusted using C1. Equivalent operational...
This circuit is from a 1995 documentation. Several CMOS integrated circuits are used to produce...