1© KEMET Electronics Corporation • P.O. Box 5928 • Greenville, SC 29606 (864) 963-6300 • www.kemet.com E5009_B-20 • 3/25/2015
One world. One KEMET
Turns and Impedance Characteristics
When the desired performance of an EMI core cannot be
obtained with a single pass through the core, the impedance
characteristics can be changed with multiple turns.
A turn is counted by the number of lead-wire windings which
pass through the inner hole of the core. Windings on the
outside of the core do not count. See Figure 1 for examples
of one, two, and three turns.
Adding turns will result in higher impedance while also
lowering the effective frequency range. See Figure 2 for an
example.
Core Material and Effective Frequency Range
There are two ferrite material options for KEMET
EMI Cores: Nickel Zinc (NiZn) and Manganese
Zinc (MnZn). Each core material has a different
resistance and effective frequency range. The MnZn
core material has a lower resistance compared to
the NiZn; therefore, adequate insulation is required
before use.
The NiZn core material is typically effective for
frequencies in the MHz band range such as the
FM-band, while the MnZn core material is typically
effective for the kHz band range such as the AM-
band. See Figure 3.
It is recommended to measure the actual frequency
range effectiveness in the target application.
EMI Cores
B-20 Series Bead Cores
Overview
KEMET B-20 Series bead cores are
designed for use on round cable. The
wide range of Manganese Zinc (MnZn)
and Nickel Zinc (NiZn) options allows for
targeting of specic frequency ranges.
EMI cores are part of a family of passive
components which address the issues
of noise or electromagnetic interference
(EMI) in circuits or systems.
Benets
• MnZn ≤ 100 MHz (AM band range)
and NiZn ≤ 300 MHz (FM band range)
options available
• Solid construction
Applications
• Consumer electronics
EMI Core
5
EMI Cores
Ring Type
　There are two materials of ferrite, Ni-Zn series and Mn-Zn ser ies. Ni-Zn series is e
ive for kHz band range.
　Note that above e band range i s a reference only. Examination of s
with actual instrument is necessary.
　As Mn-Zn series has lower resistance compared to Ni-Zn series, make sure to provide
adequate insulation before use.
Characteristics and how to count turns
　Number of turns are counted by how many times the lead wire pa sses through the inner
hole of the core. Do not count the number of lead wire winding outside the core, as it results
　When desired performance can not be obtained just b y 1 turn, impedance characteristics
value can be raised b y increasing th e turn. In this case, the e frequency band should
be checked that it is in the desired range as adding turns resu lts in lowering down the
Tips on EMI Core Usages
（Represe ntative Example：ESD-R-16C）
Fig.1　How to count turns Fig.2　Relationship between impedance an d turn counts
*Number of lead wire wound outside the core + 1
= Number of read wire passes through the inner
hole of the core
= Turn count
Mn-Zn series vs Ni-Zn series ｜Z｜-f Characteristics (representative example)
(measurement condition: measured with same-dimension ring core)
Fig.3　te
AM band range FM band range
MnZn series core
NiZn series core
Impedance (Ω)
1000
100
10
1
0.01 0.1 1 10 100 1000
Impedance Increase
Resonance point changes to lower band
3T
2T
1T
Frequency (MHz)
Impedance (Ω)
Frequency (MHz)
10000
1 10 100 1000
1000
100
10
1
3T2T1T
Figure 1 – How to count turns
EMI Core
5
EMI Cores
Ring Type
　There are two materials of ferrite, Ni-Zn series and Mn-Zn ser ies. Ni-Zn series is e
ive for kHz band range.
　Note that above e band range i s a reference only. Examination of s
with actual instrument is necessary.
　As Mn-Zn series has lower resistance compared to Ni-Zn series, make sure to provide
adequate insulation before use.
Characteristics and how to count turns
　Number of turns are counted by how many times the lead wire pa sses through the inner
hole of the core. Do not count the number of lead wire winding outside the core, as it results
　When desired performance can not be obtained just b y 1 turn, impedance characteristics
value can be raised b y increasing th e turn. In this case, the e frequency band should
be checked that it is in the desired range as adding turns resu lts in lowering down the
Tips on EMI Core Usages
（Represe ntative Example：ESD-R-16C）
Fig.1　How to count turns Fig.2　Relationship between impedance an d turn counts
*Number of lead wire wound outside the core + 1
= Number of read wire passes through the inner
hole of the core
= Turn count
Mn-Zn series vs Ni-Zn series ｜Z｜-f Characteristics (representative example)
(measurement condition: measured with same-dimension ring core)
Fig.3　te
AM band range FM band range
MnZn series core
NiZn series core
Impedance (Ω)
1000
100
10
1
0.01 0.1 1 10 100 1000
Impedance Increase
Resonance point changes to lower band
3T
2T
1T
Frequency (MHz)
Impedance (Ω)
Frequency (MHz)
10000
1 10 100 1000
1000
100
10
1
3T2T1T
Figure 2 – Relationship between impedance and turn count.
(Representative example: ESD-R-16C)
EMI Core
5
EMI Cores
Ring Type
　There are two materials of ferrite, Ni-Zn series and Mn-Zn ser ies. Ni-Zn series is e
ive for kHz band range.
　Note that above e band range i s a reference only. Examination of s
with actual instrument is necessary.
　As Mn-Zn series has lower resistance compared to Ni-Zn series, make sure to provide
adequate insulation before use.
Characteristics and how to count turns
　Number of turns are counted by how many times the lead wire pa sses through the inner
hole of the core. Do not count the number of lead wire winding outside the core, as it results
　When desired performance can not be obtained just b y 1 turn, impedance characteristics
value can be raised b y increasing th e turn. In this case, the e frequency band should
be checked that it is in the desired range as adding turns resu lts in lowering down the
Tips on EMI Core Usages
（Represe ntative Example：ESD-R-16C）
Fig.1　How to count turns Fig.2　Relationship between impedance an d turn counts
*Number of lead wire wound outside the core + 1
= Number of read wire passes through the inner
hole of the core
= Turn count
Mn-Zn series vs Ni-Zn series ｜Z｜-f Characteristics (representative example)
(measurement condition: measured with same-dimension ring core)
Fig.3　te
AM band range FM band range
MnZn series core
NiZn series core
Impedance (Ω)
1000
100
10
1
0.01 0.1 1 10 100 1000
Impedance Increase
Resonance point changes to lower band
3T
2T
1T
Frequency (MHz)
Impedance (Ω)
Frequency (MHz)
10000
1 10 100 1000
1000
100
10
1
3T2T1T
Figure 3 – Effective band range of MnZn and NiZn ferrite core material.
(Representative example, measured with same-dimension ring core)
2© KEMET Electronics Corporation • P.O. Box 5928 • Greenville, SC 29606 (864) 963-6300 • www.kemet.com E5009_B-20 • 3/25/2015
EMI Cores – B-20 Series Bead Cores
Dimensions – Millimeters
See Table 1 for dimensions
Environmental Compliance
All KEMET EMI cores are RoHS Compliant.
Table 1 – Ratings & Part Number Reference
1 Frequency range is for reference only. Please test with actual device before use.
2 Coated
Part Number
Dimensions (mm) Frequency Range1
OD ID H≤ 100 MHz
(AM band range)
≤ 300 MHz
(FM band range)
B-20F-28
2.8
1.3
3.0
X
B-20F-38
3.8
1.5
4.3
X
B-20F-46
4.6
1.5
4.3
X
B-20F-57
5.7
1.5
8.0
X
B-20L-25
2.5
1.0
1.2
X
B-20L-34
3.4
0.8
4.4
X
B -20 L- 4 4
4.4
1.6
7.0
X
B -20 L- 4 8B
4.8
2.4
4.8
X
B-20L-95B2
9.7
4.8
4.2
X
OD H
ID
3© KEMET Electronics Corporation • P.O. Box 5928 • Greenville, SC 29606 (864) 963-6300 • www.kemet.com E5009_B-20 • 3/25/2015
EMI Cores – B-20 Series Bead Cores
Impedance vs. Frequency
EMI Core
28
EMI Cores
Ring Type
Bead Type
1
10000
1000
100
10
1
10
1000
100
Impedance ()
Impedance ()
Frequency (MHz)
B-20F-28
1 10 100 1000
Frequency (MHz)
B-20F-38
1 10 100 1000
Impedance vs. Frequency
Beads Cores
OD H
ID
Shape and Dimensions
Bead Cores
[RoHS Compliant]
Bead Cores
[RoHS Compliant]
B-20F-28 2.8 1.3 3.0 ●
B-20F-38 3.8 1.5 4.3 ●
B-20F-46 4.6 1.5 4.3 ●
B-20F-57 5.7 1.5 8.0 ●
B-20L-25 2.5 1.0 1.2 ●
B-20L-34 3.4 0.8 4.4 ●
B-20L-44 4.4 1.6 7.0 ●
B-20L-48B 4.8 2.4 4.8 ●
B-20L-95B 9.7 4.8 4.2 ●(coated)
※Above frequency range is a reference only. Please test with actual device before use.
Model Dimensions (mm) Frequency range Remarks
OD ID H up to 100MHz up to 300MHz
(mainly AM band range) (mainly FM band range)
EMI Core
29
EMI Cores
Ring Type
Bead Type
1
10
1000
100
1
10
1000
100
1
10
1000
100
1
10
1000
100
1
10
1000
100
1
10
1000
100
Impedance ()
Frequency (MHz)
B-20F-46
1 10 100 1000
Impedance ()
Frequency (MHz)
B-20L-34
1 10 100 1000
Impedance ()
Frequency (MHz)
B-20L-25
1 10 100 1000
Impedance ()
Frequency (MHz)
B-20F-57
1 10 100 1000
Impedance ()
Frequency (MHz)
B-20L-44
1 10 100 1000
Impedance ()
Frequency (MHz)
B-20L-48B
Impedance ()
Frequency (MHz)
B-20L-95B
1 10 100 1000
1
10
1000
100
1 10 100 1000
Impedance vs. Frequency
EMI Core
29
EMI Cores
Ring Type
Bead Type
1
10
1000
100
1
10
1000
100
1
10
1000
100
1
10
1000
100
1
10
1000
100
1
10
1000
100
Impedance ()
Frequency (MHz)
B-20F-46
1 10 100 1000
Impedance ()
Frequency (MHz)
B-20L-34
1 10 100 1000
Impedance ()
Frequency (MHz)
B-20L-25
1 10 100 1000
Impedance ()
Frequency (MHz)
B-20F-57
1 10 100 1000
Impedance ()
Frequency (MHz)
B-20L-44
1 10 100 1000
Impedance ()
Frequency (MHz)
B-20L-48B
Impedance ()
Frequency (MHz)
B-20L-95B
1 10 100 1000
1
10
1000
100
1 10 100 1000
Impedance vs. Frequency
EMI Core
29
EMI Cores
Ring Type
Bead Type
1
10
1000
100
1
10
1000
100
1
10
1000
100
1
10
1000
100
1
10
1000
100
1
10
1000
100
Impedance ()
Frequency (MHz)
B-20F-46
1 10 100 1000
Impedance ()
Frequency (MHz)
B-20L-34
1 10 100 1000
Impedance ()
Frequency (MHz)
B-20L-25
1 10 100 1000
Impedance ()
Frequency (MHz)
B-20F-57
1 10 100 1000
Impedance ()
Frequency (MHz)
B-20L-44
1 10 100 1000
Impedance ()
Frequency (MHz)
B-20L-48B
Impedance ()
Frequency (MHz)
B-20L-95B
1 10 100 1000
1
10
1000
100
1 10 100 1000
Impedance vs. Frequency
4© KEMET Electronics Corporation • P.O. Box 5928 • Greenville, SC 29606 (864) 963-6300 • www.kemet.com E5009_B-20 • 3/25/2015
EMI Cores – B-20 Series Bead Cores
Impedance vs. Frequency Cont’d
EMI Core
29
EMI Cores
Ring Type
Bead Type
1
10
1000
100
1
10
1000
100
1
10
1000
100
1
10
1000
100
1
10
1000
100
1
10
1000
100
Impedance ()
Frequency (MHz)
B-20F-46
1 10 100 1000
Impedance ()
Frequency (MHz)
B-20L-34
1 10 100 1000
Impedance ()
Frequency (MHz)
B-20L-25
1 10 100 1000
Impedance ()
Frequency (MHz)
B-20F-57
1 10 100 1000
Impedance ()
Frequency (MHz)
B-20L-44
1 10 100 1000
Impedance ()
Frequency (MHz)
B-20L-48B
Impedance ()
Frequency (MHz)
B-20L-95B
1 10 100 1000
1
10
1000
100
1 10 100 1000
Impedance vs. Frequency
5© KEMET Electronics Corporation • P.O. Box 5928 • Greenville, SC 29606 (864) 963-6300 • www.kemet.com E5009_B-20 • 3/25/2015
EMI Cores – B-20 Series Bead Cores
KEMET Corporation
World Headquarters
2835 KEMET Way
Simpsonville, SC 29681
Mailing Address:
P.O. Box 5928
Greenville, SC 29606
www.kemet.com
Tel: 864-963-6300
Fax: 864-963-6521
Corporate Of ces
Fort Lauderdale, FL
Tel: 954-766-2800
North America
Southeast
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Tel: 407-855-8886
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Tel: 978-658-1663
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Mexico
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Note: KEMET reserves the right to modify minor details of internal and external construction at any time in the interest of product improvement. KEMET does not
assume any responsibility for infringement that might result from the use of KEMET Capacitors in potential circuit designs. KEMET is a registered trademark of
KEMET Electronics Corporation.
6© KEMET Electronics Corporation • P.O. Box 5928 • Greenville, SC 29606 (864) 963-6300 • www.kemet.com E5009_B-20 • 3/25/2015
EMI Cores – B-20 Series Bead Cores
Disclaimer
This product has been made available through a Private Label Agreement and a Development and Cross-Licensing Agreement between KEMET and NEC TOKIN to expand market
and product offerings for both companies and their respective customers. For more information, please visit http://www.kemet.com/nectokin.
All product speci cations, statements, information and data (collectively, the “Information”) in this datasheet are subject to change. The customer is responsible for checking and
verifying the extent to which the Information contained in this publication is applicable to an order at the time the order is placed.
All Information given herein is believed to be accurate and reliable, but it is presented without guarantee, warranty, or responsibility of any kind, expressed or implied.
Statements of suitability for certain applications are based on KEMET Electronics Corporation’s (“KEMET”) knowledge of typical operating conditions for such applications, but are
not intended to constitute – and KEMET speci cally disclaims – any warranty concerning suitability for a speci c customer application or use. The Information is intended for use only
by customers who have the requisite experience and capability to determine the correct products for their application. Any technical advice inferred from this Information or otherwise
provided by KEMET with reference to the use of KEMET’s products is given gratis, and KEMET assumes no obligation or liability for the advice given or results obtained.
Although KEMET designs and manufactures its products to the most stringent quality and safety standards, given the current state of the art, isolated component failures may still
occur. Accordingly, customer applications which require a high degree of reliability or safety should employ suitable designs or other safeguards (such as installation of protective
circuitry or redundancies) in order to ensure that the failure of an electrical component does not result in a risk of personal injury or property damage.
Although all product–related warnings, cautions and notes must be observed, the customer should not assume that all safety measures are indicted or that other measures may not
be required.