There is simple and good way to generate quite pure sine wave:
This circuit is not very simple, but results are quite fine: output is pure sine wave. From the other side, this schematics have some minuses: it is hard to change frequence. So this type of generator is not very usefull for variable frequence devices.
For my purpose I am using this generator to modulate RF. Here are some osciloscope shots of real world hardware:
AM modulation in it’s clasic way:
P.S. this device use dual polarity power suply.