With this circuit it is possible to vary the resistance by adjusting the mark/space reaction of the 555. The circuit was found in the November 1989 Radio Electronics magazine.
The frequency depends on the coil and is not found in the original documentation but should be...
This is a device for those who need to show that they know how to use digital electronics but have...
Using an operational amplifier with FET, this circuit from a 1977 publication can generate...