This 1/2 hertz high selectivity filter was found in the December 1990 issue of Radio Electronics magazine. The source must be symmetrical. The capacitors can be changed for other frequencies.
This circuit came out in a Popular Electronics from December 1995. It is a double T configuration that...
This low power amplifier, with 2 W in charge of 16 ohms, was found in a Japanese magazine from the...
This circuit was found in a 1967 US documentation. It shows how to build a gain control by digital...