From: sweir ([email protected])
Date: Tue Nov 07 2000 - 18:17:06 PST
Just be careful that any ferrite you choose really is sufficiently
resistive everywhere that matters to prevent peaking. Look at the
frequency curves carefully and simulate as necessary. You may be surprised
to find that you still need a damping resistor when using ferrites. It
just depends on the application.
At 03:20 PM 11/7/00 -0500, you wrote:
>Or we can be lazy/conservative, and use a ferrite bead instead of an inductor,
>so that the high-frequency noise gets turned into heat instead of getting
>reflected back to the source... I don't like using low-loss/high-Q
>in a circuit whose component values/parasitics/frequencies aren't under my
>R. Kenneth Keenan's books suggest bypassing power with series ferrite beads
>* < 10 ohms impedance at the circuit's clock frequency.
>* > 50 ohms impedance at 5 * the circuit's clock frequency.
>The high-permeability manganese-zinc ferrites are usually good up to about
>40MHz. The medium-permeability nickel- zinc ferrites are usually good up to
>200MHz, and low-permeability nickel-zinc ferrites are usually good above
>Since each company that makes ferrite beads and cores has their own system for
>naming their compositions, you usually have to look at the
>impedance-versus-frequency curves in their datasheets/catalogs to identify
> John Barnes Advisory
> Lexmark International
>**** To unsubscribe from si-list or si-list-digest: send e-mail to
>[email protected] In the BODY of message put: UNSUBSCRIBE
>si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
>si-list archives are accessible at http://www.qsl.net/wb6tpu
**** To unsubscribe from si-list or si-list-digest: send e-mail to
[email protected] In the BODY of message put: UNSUBSCRIBE
si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
si-list archives are accessible at http://www.qsl.net/wb6tpu
This archive was generated by hypermail 2b29 : Tue May 08 2001 - 14:30:00 PDT