PSN-L Email List Message

Subject: Re: ferrite use for AM radio noise suppression
From: "Charles R. Patton" charles.r.patton@........
Date: Tue, 25 Jul 2000 21:59:27 -0700

One other minor note.  Ferrite beads generally won=92t do much good at AM=

frequencies.  Their impedance doesn=92t get to 10 to 50 ohms or more =96
depends on the size and ferrite mix =96 until you=92re in the 10 to 100 M=
or more range.  Therefore the low impedance only has value in power
supply areas where there is considerable capacitance bypassing going on,
but almost no effect in the high impedance signal areas.  That=92s why I
suggested the use of resistors in the input area of the op-amp.  The
alternative would be the use of choke coils =96 expensive, relatively
harder to get, and still require a resistor to damp their resonance.

Charles R. Patton


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Larry Cochrane <cochrane@..............>