This simple circuit can work with either 4.5 V or 6 or 9 V if a 1k resistor is added in series with the set of LEDs. The circuit is from an old French publication.
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...