This circuit has an accuracy of 1%. The components used must be precision as well. The input frequency range is 40 Hz to 10 kHz with the indicated components.
We found this circuit in the March 1992 Radio Electronics magazine. The circuit provides 100 Hz...
This circuit is from old documentation. Based on two operational amplifiers of the time, it can be...
Relays from 20 mA to 200 mA can be driven by this sensitive circuit.6 or 12 V relays can be used...