This NEC commercial amplifier was manufactured in Japan in the 1960s. The circuit uses 4 transistors from the time and was powered by a 9 V battery voltage formed by large batteries.
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...