Home/Technical Glossary/Linear DC (Direct Current) Welder Linear DC (Direct Current) Welder The transistor direct current power supplies (also called Linear DC) produce much the same results as the high frequency inverter by using a high number of power transistors as the direct energy source. This technology provides clean, square wave forms with extremely fast rise time. Used primarily in constant voltage feedback control, transistor DC power supplies are effective in thin foils and fine wire welding applications and for extremely short welds. Linear DC welders utilize transistor controlled feedback enabling total feedback response times of less than 5 μS. The term Linear DC comes from the waveform that is output from the power supply. No transformer is utilized. The primary limitation to Linear DC technology is the low duty cycles, typically much less than 1 weld per second at less than rated output. For more information regarding how to choose the right power supply for your application, read our blog: AC, DC, CD or HF: Which Spot Welding Power Supply Should I Use?