Using a CA3030, this circuit was found in the May 1988 Radio Electronics magazine. The power supply must be symmetrical.
We found this configuration of band rejector filter or band rejector with operational 741 in a...
This oscillator can use any CMOS inverter. The circuit is crystal controlled and was found in the...
This circuit was found in a 1967 US documentation. It shows how to build a gain control by digital...