This circuit lets through the 300 Hz to 3kHz range that corresponds to the human voice. We found it in the Radio Electronics magazine of February 1990. The circuit uses both parts of the LM381.
This class B push-pull amplifier circuit with a few hundred milliwatts of power was found in an...
In the figure we have a window detector that uses only a voltage comparator. The circuit can use...
This circuit was found in an old American documentation. The operational used is of the...