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.
We found this circuit in a year 2000 documentation. It must be powered by a voltage of 5 V as it...
This circuit was found in the February 1990 issue of Radio Electronics magazine. The circuit uses...
Voltage comparators, such as those in the LM139/239/339 series, consist of devices that can be...