In the figure we have the way to obtain 500 gain from a FET. FETs can be BF245 or MPF102. The circuit is from the 1977 National Semiconductor FET Data Book. Power supply depends on the application.
This circuit was found in a 1980s documentation. The IC is the 7400 and should be powered with 5...
The function generator XR2206 is not very easy to obtain, but if you get one you can assemble this...
This circuit converts a 12 V continuous voltage from a battery into an alternating voltage of 110...