A real ferrite bead cross reference needs impedance at the noise frequency, not at 100 MHz by default. Walsin’s inductor export publishes exactly one frequency point, populated on 609 of 641 bead rows. The resistive/reactive split, DC bias derating and insertion loss an EMI decision needs have no column in this file at all.
Venatech Limited, an authorised Walsin distributor in Hong Kong, holds Walsin_Inductor_ALL.xlsx, Walsin Technology (Walsin)’s full parametric inductor export. We excluded the one QA test row (Test123999) and worked from the real total of 5,410 part numbers, of which 641 are ferrite beads — identified by an Ω in the Unit column rather than nH or µH. Every count below is measured from that file, and every part number is real.
How many frequency points does a ferrite bead cross reference actually need?
At least three, and usually more. A bead’s impedance is not one number — it is a curve across frequency, built from a resistive component that rises with frequency and a reactive component that peaks near self-resonance and falls after it. To cross a bead honestly you need the impedance at your actual noise frequency (which is rarely 100 MHz), the split between the resistive and reactive parts at that frequency (because only the resistive part actually dissipates the noise), the DC bias derating curve (because impedance collapses as bias current rises), and the insertion-loss figure in your actual circuit impedance. That is four separate pieces of frequency-dependent data for one honest decision.
| What a real EMI decision needs | Published in Walsin_Inductor_ALL.xlsx? |
|---|---|
| Impedance at the noise frequency, whatever it is | One fixed frequency only: 100 MHz |
| Impedance curve across multiple frequencies | No — a single column, no sweep |
| Resistive / reactive split (R vs X) at that frequency | No column exists |
| DC bias derating curve | No column exists |
| Insertion loss in a stated test circuit | No column exists |
| Rated current (thermal limit, not a bias curve) | Yes, on 611 of 641 rows |
| DC resistance | Yes, in the standard Ω notation on 634 of 641 rows |
How many frequency points does Walsin’s export publish?
One. We searched every column header in Walsin_Inductor_ALL.xlsx for a second frequency and found none — the file has 14 columns total, and Impedance (100MHz) is the only one that names a frequency anywhere in its header. 609 of the 641 bead rows carry a non-zero figure there; the other 32 read a literal zero, so even the single published frequency is incomplete.
A buyer whose actual noise problem sits at 30 MHz, 1 GHz or 2.4 GHz has no published Walsin figure at that frequency for any of the 641 beads in this file. The 100 MHz point is a reasonable mid-band reference for a general EMI survey, but it is not a substitute for the frequency the noise is actually at, and nothing in the export tells you how steeply the curve falls away on either side of it.
Does the export split impedance into its resistive and reactive parts?
No — not on any of the 641 rows. We checked all 14 columns in the file and none separates the resistive component (which dissipates the noise as heat) from the reactive component (which just reflects it). The single Impedance (100MHz) figure is the vector magnitude, |Z|, and that is the number most EMI filter selection guides warn against using alone, because a bead that is mostly reactive at your frequency behaves very differently in a circuit from one that is mostly resistive at the same |Z|.
Does the export publish DC bias derating or insertion loss for a bead?
No, for either. A ferrite bead’s impedance is not constant with DC bias current — the core approaches saturation as bias current rises, and impedance at the design frequency falls well before the rated-current thermal limit is reached. No column in Walsin_Inductor_ALL.xlsx publishes a derating curve, a percentage-of-impedance-at-rated-current figure, or an insertion-loss number in a stated test fixture. Rated current (populated on 611 of 641 bead rows) is a thermal limit, not a bias-derating curve, and the two are routinely confused because they are the only current-related figures in the file.
What happens when two beads share the same 100 MHz figure and nothing else?
They stop looking like the same part the moment you check a second field. We held one requirement steady — 2012 (0805), 600 Ω at 100 MHz — and the export returned candidates across four different series that agree on the one published frequency point and disagree everywhere else:
| Part number | Series | Size | Impedance (100 MHz) | RDC | Rated current | Match / mismatch vs 2012(0805), 600 Ω @ 100 MHz |
|---|---|---|---|---|---|---|
WLBD2012K2U601TP |
WLBD | 2012(0805) | 600 Ω | 0.3 Ω | 500 mA | Match on case and the one published frequency; mismatch — nearly double the RDC of the HC row below |
WLBD2012HCU601TH |
WLBD(HC) | 2012(0805) | 600 Ω | 0.09 Ω | 2 A | Match on case and the one published frequency; mismatch — 4x the rated current of the standard WLBD row at the identical impedance figure |
WTCF2012Z0M601PB |
WTCF | 2012 (written as a bare integer) | 600 Ω | 0.6 Ω | 240 mA | Match on the one published frequency; mismatch — RDC double the standard WLBD row, rated current under half |
WQCF2012Z0M601PB |
WQCF | 2012 (bare integer) | 600 Ω | 0.6 Ω | 240 mA | Match on the one published frequency; mismatch — identical to the WTCF row above under a different series name |
Four series, one shared published figure, and a four-to-one spread in rated current at the same case size and the same 100 MHz impedance. We will not tell you a part is equivalent on the strength of one shared figure. The export gives you one point of agreement and leaves the rest of the curve, and the current behaviour behind it, for you to confirm elsewhere.
Does any bead row publish a self-resonant frequency at all?
Only 9 of the 641. We checked the SRF(min) column across the whole bead population and found a non-zero value on exactly 9 rows, all of them in the MPA series — and those same 9 MPA rows are the ones we had already found, in an earlier pass through this file, to be microhenry power inductors mistagged with an Ω unit rather than genuine ferrite beads. So of the 632 rows that are actually beads once the mistagged MPA rows are set aside, zero publish a self-resonant frequency. We have not seen this specific subtraction counted anywhere. SRF is the figure that tells you where a bead stops behaving mainly as an inductor and starts behaving mainly as a resistor — it is central to EMI selection, and it is absent from every genuine bead row in the file.
What should an engineer send us instead of a single impedance number?
Your noise frequency, your DC bias current and your required insertion loss in your own circuit impedance — because the export cannot answer any of those three on its own.
- State the actual noise frequency, not 100 MHz by default. We can tell you honestly whether Walsin publishes a figure there; for most of the catalogue it will not, and the 100 MHz point is the only one on file.
- Cross the case size and 100 MHz figure on our free cross reference tool as a first filter. Paste up to 500 part numbers or drop an Excel or CSV, and it matches against 800,000+ crossable Walsin part numbers and states every difference field by field.
- Tell us your DC bias current. We cannot give you a derating curve from this export, but we can request the series datasheet from Walsin with that figure attached.
- Check ready stock — a dated snapshot as at 23 September 2026 — before committing a case size to a production build.
For how the Unit column separates beads from inductors in the first place, see Ferrite bead selection: 641 of Walsin’s 5,410 inductor rows are not inductors. For the self-resonant-frequency question on the inductor side of the same file, see Inductor self-resonant frequency. The full range is on the Walsin inductor range page.
The short version
A ferrite bead cross reference built only on Walsin’s export is built on one frequency, 100 MHz, populated on 609 of 641 bead rows, with no resistive/reactive split, no DC bias derating curve and no insertion-loss figure anywhere in the file. Two beads that agree on that single 100 MHz figure can differ four-to-one on rated current at the identical case size, and the one column that would describe a bead’s behaviour away from 100 MHz — self-resonant frequency — is populated on 9 rows, every one of which is a mistagged power inductor rather than a true bead. We hold no inductor or bead datasheet for any series, so we are telling you what the export cannot do rather than quoting a mechanism we have not seen.
Send us your actual noise frequency, your bias current and the case sizes you can fit, and we will come back with Walsin candidates field by field — blanks included — checked against what was physically in Hong Kong on 23 September 2026.
Frequently asked questions
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How many frequency points does Walsin’s inductor export publish for a ferrite bead?
One. The file has 14 columns in total and Impedance (100MHz) is the only one naming a frequency anywhere in its header. 609 of the 641 bead rows carry a non-zero figure there; the other 32 read a literal zero, so the single published point is itself incomplete.
Does Walsin’s export separate a bead’s resistive and reactive impedance?
No. The single Impedance (100MHz) figure is the vector magnitude, with no breakdown into the resistive part that dissipates noise and the reactive part that reflects it. We checked all 14 columns in the file and found no R/X split for any of the 641 bead rows.
Does Walsin’s export publish a DC bias derating curve for a bead?
No. No column states how impedance falls as DC bias current rises. Rated current, populated on 611 of 641 bead rows, is a thermal limit rather than a derating curve, and the two figures should not be substituted for each other.
Can two Walsin ferrite beads share the same 100 MHz impedance and differ everywhere else?
Yes. Four series — WLBD, WLBD(HC), WTCF and WQCF — each publish a 2012 (0805) bead at exactly 600 Ω at 100 MHz, and the rated current across those four spans 240 mA to 2 A, a four-to-one difference at the identical case size and the identical published frequency point.
Does any Walsin bead row publish a self-resonant frequency?
Only 9 of 641, and every one of those 9 is in the MPA series, which we had already identified as microhenry power inductors mistagged with an ohm unit rather than genuine ferrite beads. Once those are set aside, zero of the 632 rows that are actually beads publish a self-resonant frequency.
Does Venatech hold a datasheet that fills in the missing ferrite bead curves?
No. We hold 28 Walsin datasheets, 451 pages, covering 26 MLCC series and 2 chip resistor series. Not one covers an inductor or bead family, so every figure in a Walsin bead cross reference we write comes from the export alone, and we say so rather than implying coverage we do not have.
What should I send Venatech for a ferrite bead cross reference instead of one impedance figure?
Your actual noise frequency, your DC bias current and the case sizes your board can fit. The export can tell you the 100 MHz impedance, the DC resistance and the rated current on most rows, but it cannot answer a bias or frequency question outside 100 MHz, so those three inputs from you are what let us ask Walsin the right follow-up question.