12 Volt Automotive Inverter : This circuit will allow you to operate small devices like laptop computers inside your automobile without an expensive automobile power supply. The circuit takes advantage of the fact that power transformers are linear devices and can be used to step up as well as step down.

12 Volt DC to 120 Volt AC Inverter: this inverter should solve that problem. It takes12 VDC and steps it up to120 VAC. The-Wattage depends on which transistors you use for Q1 and Q2, as well as how "big" a transformer you use for T1. The inverter can be constructed to supply anywhere from1 to1000 (1 KW)-Watts. 

DC to AC Inverter:

Digital to Analog Centronics D / A & Filter: