Choosing the Right EMC Ferrite

Choosing the Right EMC Ferrite

This article from Würth outlines six types of ferrites and helps you select the best ferrite for your design. There are a wide variety of EMC ferrites to choose from.

Types of EMC Ferrites

Snap ferrites from Würth Elektronik

The snap ferrites of Würth Elektronik are suited for retrospective fitting on existing cable lines. The special lock, the so-called key technology, on the Würth Elektronik snap ferrites offers assurance against unauthorised opening – cue CE mark. At the same time, the plastic case protects against mechanical damage and its construction offers increased contact pressure on the ferrite halves.

The result is very high impedance, or in other words interference suppression. Typical applications are signal lines, monitor leads, printer cables, mouse cables, data transmission lines etc.

View these products on the Digi-Key Website.

Ferrite sleeves and ferrite rings

Unlike snap ferrites or ferrites with nylon clamps, the ferrite sleeves or rings can be slid onto the cable prior to final assembly and fixed by using a heat shrinking tube or potting process. This solution is found on every computer monitor today. The closer the inner diameter is adapted to the cable diameter, the greater the suppression effect. Also with multiple winding turns, as with snap ferrites, the inductive part can be emphasised while achieving greater impedance.

View these products on the Digi-Key Website.

6-hole ferrite beads

The 6-hole beads – commonly known as VHF chokes – or our SMD type WE-SUKW (5-hole ferrite bead) usually come with 2.5 windings and withstand high levels of current over long periods without going into saturation. They achieve effective RF interference suppression directly on the board. Typical applications are ground decoupling, supply voltage decoupling in association with blocking capacitors and data line filters.

View these products on the Digi-Key Website.

Multiline ferrites

The multiline ferrite is a universally applicable suppression component: Firstly as a 4-turn current- compensated choke with a high current rating of typically 4 A. The impedance or the current can be increased with the appropriate circuit. Furthermore, a dual current-compensated wideband choke can also be achieved with the right connection (cf. Fig. 1).

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View these products on the Digi-Key Website.


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SMD Ferrites of Würth Elektronik

Current is also passed through the ferrite in the SMD ferrites; for the signal, it acts as a low impedance connection (RDC → 0 Ω); however for the interference spectrum as a high loss resistance (impedances up to 5 kΩ).

With a multilayer construction current loads up to 6 A are achievable depending on the ferrite design. The following sizes are available 0402, 0603, 0805, 1206, 1210, 1806 and 1812 as standard.

In the pre-design stage, the engineer can design short-circuited solder pads at critical points, which can be separated and the appropriate SMD ferrites mounted after EMC measurement.

View these products on the Digi-Key Website.


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Choosing the right ferrite

The correct choice of ferrite can only be confirmed by measurements in the EMC lab. The calculation of the dynamic impedance (system impedance) of a high frequency electronic circuit is generally not possible. This is dependent on many factors, which are hard to describe mathematically, especially in the RF range.

Nevertheless, initial selection can be made with comparative measurements and experience:

Supply voltage lines and ground lines have a circuit impedance in the range 1–10 Ω, useful signal lines again have a circuit impedance between 50–100 Ω and video, clock and data lines have higher circuit impedance depending on the application (e.g. bus systems such as CAN, SCSI etc.)

Starting from this system impedance (ZA and ZB) and the required interference suppression, the ferrite impedance (ZF) can be calculated by using the equation above. According to the impedance of the ferrite and the application the correct part can be chosen now, e.g. a ferrite sleeve or an SMD ferrite.

Ferrite Design Kits

Want to learn more about Ferrites? Visit the Würth catalog where you can purchase one of their ferrite design kits and ask questions from the ferrite experts.

View these products on the Digi-Key Website.


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Information and media in this post was provided by Würth Elektronik.


Applicable Part Numbers
DK Part # Mfr Part # Description Series
732-10084-ND 742700 EMI SUPPRESSION AXIAL FERRITE BE WE-AFB
732-10085-ND 742711 SNAP FERRITES -
732-10086-ND 742841 SMD FERRITES WE-CBF HF WE-CBF
732-10146-ND 744230 SMD COMMON MODE LINE FILTERS WE- WE-CNSW
732-10147-ND 744630 COMMON MODE POWER LINE CHOKES WE WE-LF
732-10148-ND 744725 SMD COMMON MODE LINE FILTERS -
732-10150-ND 744800 COMMON MODE POWER LINE CHOKES WE WE-CMBNC
732-10151-ND 744821 COMMON MODE POWER LINE CHOKES WE WE-CMB
732-10152-ND 744825 COMMON MODE POWER LINE CHOKES WE WE-CMB, WE-CMBH
732-10153-ND 782013 AXIAL EMI SUPPRESSION FERRITES W Automotive, AEC-Q200, WE-AEFA
732-10154-ND 782792 SMD EMI SUPPRESSION FERRITE BEAD WE-CBA
732-10180-ND 760801 POWER FACTOR CORRECTION CHOKES W WE-PFC
732-11546-ND 74271151 FERRITE 417OHM HINGED 15.01MM Star-Tec
732-11547-ND 74271151S FERRITE 417OHM HINGED 15.01MM Star-Tec
732-11548-ND 74271251 FERRITE 525OHM HINGED 24.99MM Star-Tec
732-11549-ND 74271251S FERRITE 525OHM HINGED 24.99MM Star-Tec
732-13172-ND 74271733S SNAP FERRITE W/FLEXIBLE CABLE FI Star-Fix
732-13448-ND 74272142 STAR-TEC LFS SNAP FERRITE WITH S Star-Tec LFS
732-13457-ND 74272131 STAR-TEC LFS SNAP FERRITE WITH S Star-Tec LFS
732-13458-ND 74272132 STAR-TEC LFS SNAP FERRITE WITH S Star-Tec LFS
732-13459-ND 74272151 STAR-TEC LFS SNAP FERRITE WITH S Star-Tec LFS
732-13460-ND 74272211 STAR-TEC LFS SNAP FERRITE WITH S Star-Tec LFS
732-13461-ND 74272221 STAR-TEC LFS SNAP FERRITE WITH S Star-Tec LFS
732-13462-ND 74272222 STAR-TEC LFS SNAP FERRITE WITH S Star-Tec LFS
732-13463-ND 74272251 STAR-TEC LFS SNAP FERRITE WITH S Star-Tec LFS
732-13464-ND 7427014 WE-TOF EMI SUPPRESSION TOROIDAL WE-TOF
732-13466-ND 74270051 WE-AFB EMI SUPPRESSION AXIAL FER WE-AFB
732-13468-ND 74271633 STAR-GAP SNAP FERRITE FOR RF APP WE-STAR-GAP
732-13478-ND 7427141 SNAP-RING SNAP FERRITE WITH PLAS Snap-Ring
732-13480-ND 742701716 WE-TOF EMI SUPPRESSION TOROIDAL WE-TOF
732-13483-ND 74271622 STAR-GAP SNAP FERRITE FOR RF APP WE-STAR-GAP
732-13485-ND 742724759 STAR-FLAT SNAP FERRITE WITH SAFE WE-FLAT
732-13783-ND 7427502 WE-UKW EMI SUPPRESSION 6-HOLE FE WE-UKW
732-13784-ND 74275043 WE-UKW EMI SUPPRESSION 6-HOLE FE WE-UKW
732-13785-ND 7427504 WE-UKW EMI SUPPRESSION 6-HOLE FE WE-UKW
732-13786-ND 7427501 WE-UKW EMI SUPPRESSION 6-HOLE FE WE-UKW
732-13787-ND 74275013 WE-UKW EMI SUPPRESSION 6-HOLE FE WE-UKW
732-13788-ND 7427503 WE-UKW EMI SUPPRESSION 6-HOLE FE WE-UKW
732-13789-ND 74275022 WE-UKW EMI SUPPRESSION 6-HOLE FE WE-UKW
732-13997-ND 742722 FLAT FERRITE CORES WE-FLAT WE-FLAT
732-14008-ND 74271722S STAR-FIX SNAP FERRITE WITH FLEXI Star-Fix
732-1499-ND 7427246 FERRITE CORE 194 OHM HINGED Star-Flat
732-1500-ND 7427247 FERRITE CORE 192 OHM HINGED Star-Flat
732-1501-ND 7427248 FERRITE CORE 180 OHM HINGED Star-Flat
732-1502-ND 74272475 FERRITE CORE 114 OHM HINGED Star-Flat
732-1503-ND 74271112 FERRITE CORE 321 OHM HINGED 6MM Star-Tec
732-1504-ND 74271131 FERRITE CORE 246 OHM HINGED Star-Tec
732-1505-ND 74271132 FERRITE CORE 241 OHM HINGED Star-Tec
732-1506-ND 74271221 FERRITE CORE 270 OHM HINGED Star-Tec
732-1507-ND 74271222 FERRITE CORE 265 OHM HINGED Star-Tec
732-1508-ND 7427153 FERRITE CORE 165 OHM HINGED 8MM Star-Ring
732-1509-ND 7427151 FERRITE CORE 119 OHM HINGED Star-Ring
732-1510-ND 7427154 FERRITE CORE 130 OHM HINGED 16MM Star-Ring
732-1511-ND 7427155 FERRITE CORE 110 OHM HINGED 27MM Star-Ring
732-1513-ND 74271622S FERRITE CORE 140 OHM HINGED Star-Gap
732-1514-ND 74271633S FERRITE CORE 100 OHM HINGED 8MM Star-Gap
732-1515-ND 74270111 FERRITE CORE 50 OHM SOLID 3.3MM WE-TOF
732-1517-ND 742701121 FERRITE CORE 123 OHM SOLID 5MM WE-TOF
732-1520-ND 74270162 FERRITE CORE 94 OHM SOLID 6.76MM WE-TOF
732-1522-ND 74270117 FERRITE CORE 161 OHM SOLID 10MM WE-TOF
732-1540-ND 74270033 FERRITE CORE 162 OHM SOLID WE-AFB
732-1541-ND 74270030 FERRITE CORE 158 OHM SOLID 5MM WE-AFB
732-1545-ND 74270037 FERRITE CORE 199 OHM SOLID 5.6MM WE-AFB
732-1551-ND 74270034 FERRITE CORE 160 OHM SOLID 7.3MM WE-AFB
732-1553-ND 74270052 FERRITE CORE 170 OHM SOLID 8MM WE-AFB
732-1558-ND 74270091 FERRITE CORE 170 OHM SOLID 9.5MM WE-AFB
732-1644-ND 742792 KIT DESIGN FERRITE CHIP BEAD WE-CBF
732-1913-ND 74271722 FERRITE CORE 270 OHM HINGED Star-Fix
732-1914-ND 74271733 FERRITE CORE 246 OHM HINGED 8MM Star-Fix
732-1915-ND 742791 KIT FERRITE SMD 1206-1812 SIZES WE-CBF
732-1916-ND 742790 KIT FERRITE SMD 0402-0805 SIZES WE-CBF
732-1920-ND 744864 KIT CHOKE FC SERIES WE-FC
732-2395-ND 7427221 FERRITE CORE 166 OHM SOLID WE-FLAT
732-2404-ND 74272733 FERRITE CORE 62 OHM HINGED 8MM STAR-FIX LFS
732-2405-ND 742730021 FERRITE BEAD 170 OHM RADIAL 4LN WE-MLS
732-2406-ND 742730022 FERRITE BEAD 248 OHM RADIAL 4LN WE-MLS
732-2407-ND 74273002 FERRITE BEAD 249 OHM RADIAL 4LN WE-MLS
732-2408-5-ND 74273001 FERRITE BEAD 264 OHM RADIAL 3LN WE-MLS
732-2409-5-ND 742730023 FERRITE BEAD 334 OHM RADIAL 4LN WE-MLS
732-3086-ND 74272722 FERRITE CORE 40 OHM HINGED STAR-FIX LFS
732-3090-ND 7427727 FERRITE CORE 100 OHM SOLID WE-AFB LFS
732-3302-ND 74275812 FERRITE CORE 200 OHM HINGED 5MM STAR-BUENO
732-3303-ND 74275813 FERRITE CORE 200 OHM HINGED STAR-BUENO
732-3304-ND 74275815 FERRITE CORE 350 OHM HINGED STAR-BUENO
732-3419-ND 74271142 FERRITE CORE 182 OHM HINGED 5MM Star-Tec
732-3420-ND 74271142S FERRITE CORE 182 OHM HINGED 5MM Star-Tec
732-3617-ND 7427153S FERRITE CORE 165 OHM HINGED 8MM Star-Ring
732-3619-ND 74271222S FERRITE CORE 265 OHM HINGED Star-Tec
732-3621-ND 74271221S FERRITE CORE 270 OHM HINGED Star-Tec
732-3623-ND 74271132S FERRITE CORE 241 OHM HINGED Star-Tec
732-3625-ND 74271131S FERRITE CORE 246 OHM HINGED Star-Tec
732-3627-ND 74271112S FERRITE CORE 321 OHM HINGED 6MM Star-Tec
732-3629-ND 74271111S FERRITE CORE 320 OHM HINGED 5MM Star-Tec
732-3635-ND 7427151S FERRITE CORE 119 OHM HINGED Star-Ring
732-3636-ND 7427155S FERRITE CORE 110 OHM HINGED 27MM Star-Ring
732-3637-ND 7427154S FERRITE CORE 130 OHM HINGED 16MM Star-Ring
732-3977-ND 74270024 FERRITE CORE 119 OHM SOLID WE-SAFB
732-3978-ND 74270023 FERRITE CORE 160 OHM SOLID 4MM WE-SAFB
732-3979-ND 742700221 FERRITE CORE 45 OHM SOLID 4MM WE-SAFB
732-3980-ND 74270022 FERRITE CORE 59 OHM SOLID 4MM WE-SAFB
732-3981-ND 74270021 FERRITE CORE 88 OHM SOLID 3MM WE-SAFB
732-3982-ND 74270020 FERRITE CORE 108 OHM SOLID 2.4MM WE-SAFB
732-3983-ND 7427002 FERRITE CORE 125 OHM SOLID 1.2MM WE-SAFB
732-3985-ND 74270015 FERRITE CORE 95 OHM SOLID 2MM WE-SAFB
732-3992-ND 742700726 FERRITE CORE 278 OHM SOLID 4MM WE-SAFB
732-3993-ND 7427007141 FERRITE CORE 45 OHM SOLID 2MM WE-SAFB
732-3996-ND 74271111 FERRITE CORE 320 OHM HINGED 5MM Star-Tec
732-7427143-ND 7427143 SNAP-RING SNAP FERRITE -
732-7427144-ND 7427144 SNAP-RING SNAP FERRITE -
732-78271111-ND 78271111 CAR-TEC SNAP FERRITE ; 316 ; 3.5 WE-CAR-TEC
732-78271111S-ND 78271111S CAR-TEC SNAP FERRITE ; 316 ; 3.5 WE-CAR-TEC
732-78271112-ND 78271112 CAR-TEC SNAP FERRITE ; 316 ; 4.5 WE-CAR-TEC
732-78271112S-ND 78271112S CAR-TEC SNAP FERRITE ; 316 ; 4.5 WE-CAR-TEC
732-78271131-ND 78271131 CAR-TEC SNAP FERRITE ; 235 ; 6.0 WE-CAR-TEC
732-78271131S-ND 78271131S CAR-TEC SNAP FERRITE ; 235 ; 6.0 WE-CAR-TEC
732-78271132-ND 78271132 CAR-TEC SNAP FERRITE ; 235 ; 7.0 WE-CAR-TEC
732-78271132S-ND 78271132S CAR-TEC SNAP FERRITE ; 235 ; 7.0 WE-CAR-TEC
732-9640-ND 74271211 FERRITE CORE 425 OHM HINGED 21MM Star-Tec
732-9641-ND 74271211S FERRITE CORE 425 OHM HINGED 21MM Star-Tec
7427114-ND 7427114 FERR SLV SNAP W/CASE 5.0MM GRY SNAP-SLEEVE
7427122-ND 7427122 FERRITE CORE 273 OHM HINGED -
‎74271833-ND‎ 74271833 FERRITE CORE 113 OHM HINGED 8MM Star-Gap