ferrite beads

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ok, i frequently read ferrite beads should be used in IC power supply line.

some questions: why not use small inductors like http://www.reichelt.de/bilder/web/B400/!SMCC.jpg
?

and for the beads, i got some AMIDON beads http://www.reichelt.de/bilder/web/B400/T20.jpg

diameter 6,48 mm
inner diameter 3,05 mm
thick 2,44 mm
AL (µH/100Wdg): 34
MHz max.: 30

and enamelled copper wire 0,6 mm diameter.

So how many windings of wire should i make with the wire trough the bead? Or what values of those inductors of the kind package looking like resistors? Shoul the ferrite bead near to IC like the capacitors, or should it be near to power supply to filter HF coming from powerline, regulators etc. ? What about a Filter chain like 1000uF, 100R, 220uF, 100uH, 220uF,ferrite bead, 10uF+100nf at IC?
 
Hate to tell you this, but.........

It looks like what you have there is not a ferrite, but a powdered iron toroid, used for winding inductors.

Ferrites beads are usually specified as to what ferrite mix they are made of. Toroids for inductors are usually specified as to "max useful frequency", and uH/x turns.

A ferrite bead should be either a type 43 or 73 mix. There are a few other mixes that they are made with, but are not as common. Unless the supplier can tel you which mix, do not buy them unless you have lots of experience.


Jocko
 
Thanks for information. Its no problem, i got 10 of those "wrong" beads/torroids for free. Whatever i will do with them... I have no problem to get some ferrites with type 43,61,or 77 .

But please give me information how many windings i need, or what values for inductors, to make the power supply line for a DAC / AD1865NK.

My problem is not to get the right parts if i´m told which ones, but i have no information about values to use or a schematic to looks at.

In other words, i lack the experience you mention.
 
Ferrite Beads

Bricolo said:
Jocko, I haven't found tha material used in the chokes I use
are they any good?

Bricolo,
If look at the graphs in the paper you submitted you will see that the BL02RN2 offer excellent attenuation at "CD frequencies".
Guido Tent is suggesting BLM31A J601SN1 also from Murata. These are SMD beads. (Farnell part# 581094)
No more hints from me, remember you are the student in electronics, I am just the bloody chemist.:angel:
 
which coils, the SMCC ones, or the toroids Jocko allready told me are useless? What frequencies are we talking about?

- So how many windings of wire should i make with the wire trough the bead?

- Or what values of inductors is needed?

- Should the ferrite bead near to IC like the capacitors, or should it be near to power supply to filter HF coming from powerline, regulators etc.?

- What about a Filter chain like 1000uF, 100R, 220uF, 100uH, 220uF,ferrite bead, 10uF+100nf at IC?
 
Yes, but:
- So how many windings of wire should i make with the wire trough the bead?

- Or what values of inductors is needed?

- Should the ferrite bead near to IC like the capacitors, or should it be near to power supply to filter HF coming from powerline, regulators etc.?

- What about a Filter chain like 1000uF, 100R, 220uF, 100uH, 220uF,ferrite bead, 10uF+100nf at IC?
 
for good high frequency attenuation you only use 1 pass thru the bead, not "turns"

when the ends of the wire (or worse, adjacent turns) get close together they have capacitive coupling that shorts out the inductive/resistive impedance from the ferrite - check out "self-resonant frequency" for multiturn inductors

its better to use more (or larger) beads (with a hole that barely passes your wire) on a straight wire than to try to increase inductance with extra turns - some multi hole beads are made to get higher loss in a small space but the rule is still one pass of the wire thru each hole
 
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