This circuit recognizes a tone determined by the tuned input circuit (R3 / R4 / C2). The circuit was found in Radio Electronics from the 90s. The 4046 is not a common component today.
This adjustable circuit from 0 to 200 nA was found in a 90's EDN. The components can still be...
We found this circuit in 2005 Linear Technology documentation. MPOSFET is load-matched. The...
This circuit generates audio tones in a speaker with controlled frequency and volume. The...