Wurth WE-SAFB Series Ferrite Bead Wurth Elektronik WE-SAFB Series Small-size EMI suppression ferrite beads are made from NiZn a material which works in a broad frequency range. These ferrite beads have an operating temperature of -25°C to +125°C. The applications WE-SAFB series are used for: transistor bases for feed line. Avoiding radio frequency interferences in switching amplifiers, in power electronics for IGBT – and thyristor circuits.