Found in American documentation from the 1990s, this circuit generates a whistling sound when applied to an amplifier. The power supply must be symmetrical.
This step of good gain was obtained in an American publication of the 1980s. The circuit can be...
This two-transistor circuit was found in the January 1994 issue of Electronics Now magazine....
We found this circuit in an Australian documentation from 1991. The circuit is suitable for SMD...