This simple circuit is powered by the logic circuit itself. Components are still common, although they were obtained from somewhat old documentation.
This old 1967 audio preamp uses germanium transistors. It was found in Japanese documentation at...
In the figure we have the conventional configuration of a filter that allows only the frequencies above...
This circuit is from a 1995 Electronics Now. It generates a 1 kHz sinusoidal signal. See in the...