This bargraph circuit using LM3914 was found in the October 1980 Radio Electronics magazine. Note the use of a transistor to modify the response.
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...