How to Build a 12 Vdc - 120 Vac Inverter Circuit Diagram . An Inverter is a device that converts 12 volts d.c to 120 volts a.c. , which is what we use in our homes. This project will handle about 300 watts, which is perfect for lights, small T.V.'s and radio equipment. This Inverter takes 12 volt d.c and steps it up to 120 volt a.c. The wattage depends on which transistors you use for Q1 and Q2, as well as the "Amp Rating" of the transformer you use for T1. This inverter can be constructed to supply anywhere from 1 to 1000 (1 KW) watts. If Q1, Q2 are 2N3055 NPN Transistors and T1 is a 15 A transformer, then the inverter will supply about 300 watts. Larger transformers and more powerful transistors can be substituted for T1, Q1 and Q2 for more power. Note: Don't try to run inductive loads (motors...) off this inverter . 12 Vdc - 120 Vac Inverter Circuit Diagram Parts: C1, C2 68 uf, 25 V Tantalum Capacitor R1, R2 ...