SMB/SMD case ferrite inductor identification?

[Chris56000]

Hi!

Can anyone suggest, for completeness, a method of finding out the maker/type number of a ferrite bead that looks physically like an SMB package diode?

Is measurement of physical size the only convenient way?

They're used in a power supply in series with fast–recovery SOD–80 diode rectifiers, and needless to say, totally devoid of markings!

Unfortunately I'm not an EMC or RF design expert and I'm bemused at the sheer number of these things in different packages, types, impedances, etc., etc.,

The two I found that most closely matched the things I had were:–

https://uk.rs-online.com/mobile/p/ferrite-beads/4673494/

or the Fastron SMB/001–999X–01

I've worked out a suitable circuit–symbol to document them with, but even I can't identify the exact type originally fitted it would be nice to suggest the most likely candidate on a circuit–diagram!

Chris Williams

[T3sl4co1l]

If there's no markings, there's no markings...

So, molded and leaded?  Seems like I've seen a lot of Panasonic parts turn up like that.  No idea.

Really what matters though, measure its impedance at a few spot frequencies (100MHz being the most common choice).  If you can break away the plastic to see what size the core is, that'll give you an idea what equivalent chip size to use.

If it's not encapsulated but a naked core like the Fair-Rite part pictured, mind that it matters if it's gapped or not.  The gap may be thin and hard to see.  Gap means it's an inductor, i.e., probably doesn't saturate under load current.

Tim

[Chris56000]

Hi!

Oh dear, that needs a V.N.A. and I can't run to one of those in the rest of my lifetime and the next. . .!!

Is there any cheap means of measuring impedance @ 100MHz?

Chris Williams