Figure (a) shows an example of an IGBT application circuit. Surge voltage is generated when the IGBT turns off while it is carrying the load current. Surge voltage is caused by a sharp change in IGBT current (-diC/dt) as well as the package and wire stray inductance (LS). At this time, VCEP = LS・diC/dt＋VCC is applied to the IGBT instantaneously. The IGBT is permanently damaged if a voltage exceeding its breakdown voltage is applied. A primary solution for this is to reduce the stray inductance (LS) of the main current path. It is therefore necessary to increase the width and reduce the length of the wires. If it is difficult to reduce stray inductance, the switching speed of the IGBT should be reduced by increasing the value of an external gate resistor connected in series with the gate. Care should be exercised, however, because this causes its switching loss to increase. Surge voltage can also be reduced by inserting a snubber circuit between the collector and emitter terminals of the IGBT. However, the snubber circuit causes charge/discharge loss, increasing overall circuit loss.