Circuit approaches to increasing IGBT switching speed

Circuit techniques which greatly speed up the turn-off process of the insulated-gate bipolar transistor (IGBT) are presented. The circuits apply voltage to an external capacitor while the IGBT is in the ON state, and use this voltage to extract the excess charge stored in the base region of the device when the gate is turned off. An n⁺ diffusion has been added to the n^- base to facilitate this extraction. The circuitry does not affect the intrinsic ON resistance of the IGBT and thus avoids the usual ON-resistance/switching-speed trade-off. The area associated with the n⁺ diffusion adds to the area of the IGBT, and thus increases the specific ON resistance of the device. Test devices have been fabricated and turn-off times of 500 ns have been achieved