This is the schematic diagram of 300W power inverter circuit. The circuit use timer IC NE555 as to produce the wave / AC voltage signal. The signal the fed to the final amplifier to be amplified and to powered up the signal. There are many 2SD1047 transistor to amplify the signal. The transformer used to increase the voltage level to 110V or 220 refer to your needs.
This 300W power inverter originally use 12V DC battery as the input and you’ll get 220V AC voltage.