This circuit operates from 20 Hz to over 20 kHz and is easily tunable. We found it in a 70s documentation. The circuit can be implemented with modern operational amplifiers.
This circuit lets through the 300 Hz to 3kHz range that corresponds to the human voice. We found it...
This complementary circuit increases the output power of an operational amplifier. Outputs with...
In the figure below we have an interesting circuit for those with a project that requires a...