[SI-LIST] Re: Ferrite Beads on Differential Signal Lines?

  • From: steve weir <weirsi@xxxxxxxxxx>
  • To: Randy Dawson <rdawson16@xxxxxxxxxxx>, "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
  • Date: Fri, 12 Sep 2014 14:55:43 -0700

Please take pictures of little Gina at the EMC test range demonstrating 
her prowess with her beads.
Steve.

On 9/12/2014 2:41 PM, Randy Dawson wrote:
> 'The National Ferrite Bead Association'
> I will have to put little Gina onto that resource, she has several 
> bead projects, different color ferrites, she is all over the spectrum.
>
> > Date: Fri, 12 Sep 2014 14:30:16 -0700
> > From: weirsi@xxxxxxxxxx
> > To: si-list@xxxxxxxxxxxxx
> > Subject: [SI-LIST] Re: Ferrite Beads on Differential Signal Lines?
> >
> > While often abused, ferrite beads are a tool that have legitimate
> > purposes. What makes no sense is to either:
> >
> > 1) "Solve" a problem that doesn't exist, or
> > 2) Solve a problem with inappropriate means.
> >
> > Ferrite beads are very useful in these sorts of situations:
> >
> > 1) As part of a properly decoupled high insertion loss filters.
> > 2) As components in EMI filters.
> >
> > Places where they should not be used, or at least not used alone:
> >
> > 1) As power feeds to broadband amplifiers. (All digital logic devices
> > qualify as broadband amplifiers.)
> > 2) In circuits where their low to medium frequency behavior of a high Q
> > linear inductor has not been fully considered.
> >
> > Unfortunately, there have been many times that people have misused
> > ferrite beads creating bigger problems than the beads were intended to
> > solve.
> >
> > The National Ferrite Bead Association reminds us:
> >
> > "Ferrite beads don't kill designs. Lazy engineers do."
> >
> > Best Regards,
> >
> >
> > Steve
> >
> > On 9/12/2014 8:15 AM, Lee wrote:
> > > It makes no sense to put ferrite beads in any signal line. How did 
> this get
> > > started?
> > >
> > > -----Original Message-----
> > > From: Craig Francis
> > > Sent: Thursday, September 11, 2014 4:11 PM
> > > To: si-list@xxxxxxxxxxxxx
> > > Subject: [SI-LIST] Ferrite Beads on Differential Signal Lines?
> > >
> > > SI-List,
> > > I haven't seen any literature concerning using ferrite beads on 
> each signal
> > > line of a differential pair.
> > > Usually only a common-mode choke is used to reduce common-mode EMI.
> > >
> > > Can ferrite beads be used on a differential pair to increase the 
> the rise
> > > time of the signal and reduce unnecessary high-frequency content 
> that may
> > > radiate?
> > >
> > > The two ferrite beads would be sized to allow the bandwidth 
> necessary for
> > > the differential signal's highest data rate.
> > >
> > >
> > > Thanks,
> > > Craig Francis
> > >
> > >
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> > --
> > Steve Weir
> > IPBLOX, LLC
> > 1580 Grand Point Way
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-- 
Steve Weir
IPBLOX, LLC
1580 Grand Point Way
MS 34689
Reno, NV  89523-9998
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(775) 299-4236 Business
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All contents Copyright (c)2013 IPBLOX, LLC.  All Rights Reserved.
This e-mail may contain confidential material.
If you are not the intended recipient, please destroy all records
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