Found in a 90s Radio Electronics, this circuit uses a ceramic capacitor (C1) as a sensor. The operational amplifier is a double 741 of the time.
Found in a 90's EDN, this circuit changes the phase of a signal from 50 to 60 Hz in 120 degrees. The...
The circuit shown in the figure can generate signals of good intensity up to a frequency of 30...
The MC1455 integrated circuit consists of a version of the 555 made by Motorola. The circuit given...