Using 3 ports, this rectangular oscillator was found in the March 1996 issue of Electronics Now magazine. The maximum frequency is a few megahertz, determined by R1 and C1.
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...