Semiconductor fuses are fuses that have been specifically designed to protect semiconductor devices. They are often also referred to as solid state fuses, rectifier fuses or ultra-rapid fuses. Semiconductor devices are extremely sensitive to current fluctuations and require special protection. To perform this function, semiconductor fuses are able to open the circuit (blow) significantly quicker than other fuse types, and it is extremely important that they are replaced by direct equivalents when required. Semiconductor fuses belong to the utilisation categories aR, gR and gS.