Bead, ferrite

Figure 7-4 Damping Out the High AV/At Wiggle by Inserting a Small Lossy Ni-Zn Ferrite Bead... 

To control EMI, ferrite beads (preferably of lossy nickel-zinc material) are sometimes placed in series with catch diodes (often slipped on to their leads), such as at the output diode of a typical off-line flyback. However, these beads must be very small, as they can have a significant effect on the efficiency of the power supply. 

To reduce this problem, most manufacturers add small series resistors and capacitors to ground at the input terminals. Inductors also may be added, but they are susceptible to external magnetic fields. If package shielding is inadequate, the inductors may, in fact, pick up as much noise as they are supposed to filter out. Another RFI defense consists of placing donut-shaped ferrite beads on the input leads of affected stages. 

Fig. 3 Ln-ln plot of beads per ceU versus number of cells depleted for depletion of WBCs from a leuko-rich sample (buffy-coat) of whole blood with CD45 antibody-conjugated magnetic beads. Three curves on left-hand side represent depletion runs with Rhone-Poulenc magnetic latex beads on right-hand side are runs with manganese ferrite beads. Samples analyzed were blood from donors 50080 and 49046, and 49046 after depletion of 98% platelets with CD41 antibody-conjugated beads...

Fig. 7 Graphs of beads per cell versus number of cells depleted from whole blood with CD45, CD16b, CD235a, and CD41 antibody-conjugated manganese ferrite beads (left to right, top to bottom, respectively) as determined by flow cytometry and/or hematology(ceU counter)...

---