Bourns 8120 Common Mode Choke Equivalent & Substitute Parts

Part Overview

The Bourns 8120 is a 2.4 mH, 2-line common mode choke rated for 17A maximum current with 8mOhm DC resistance, designed for through-hole mounting in vertical orientation. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement. The 8120 series operates across -55°C to 105°C and is packaged in a vertical 4-pin configuration with dimensions of 1.700" L × 0.900" W (43.18mm × 22.86mm).

Key Parameters

Parameter	Value
Inductance @ Frequency	2.4 mH @ 1 kHz
Number of Lines	2
Current Rating (Max)	17A
DC Resistance (DCR) (Max)	8mOhm
Operating Temperature Range	-55°C ~ 105°C
Mounting Type	Through Hole
Package / Case	Vertical, 4 PC Pin
Size / Dimension	1.700" L × 0.900" W (43.18mm × 22.86mm)
Height (Max)	1.650" (41.91mm)

Substitute Part Grouping Explanation

Substitute parts for the Bourns 8120 are classified into two categories based on electrical and mechanical parameter alignment:

Direct Equivalent (8120-RC): Maintains identical electrical specifications—2.4 mH inductance, 17A current rating, and 8mOhm DCR—with matching physical dimensions and through-hole vertical mounting. The primary distinction is product status: 8120-RC is active, whereas the original 8120 is obsolete. Packaging differs (bulk vs. standard), and RoHS compliance has been upgraded to ROHS3.

Parametric Equivalent (8121-RC): Shares the same series, mounting type, physical dimensions, and operating temperature range. However, electrical parameters differ: inductance is reduced to 1 mH, current rating is increased to 20A, and DCR is reduced to 7mOhm. This part is suitable for applications where lower inductance and higher current capacity are acceptable trade-offs.

Similar Substitute (CMT-8120 by Triad Magnetics): Matches the Bourns 8120 in inductance (2.4 mH), current rating (17A), and DCR (8mOhm). Differs in manufacturer, series designation, and includes additional certifications (CSA, IEC, UL, VDE) and AC voltage rating (1500V). Physical dimensions and mounting type are identical.

Parameter Comparison

Parameter	Bourns 8120 (Original)	Bourns 8120-RC (Direct Equivalent)	Bourns 8121-RC (Parametric Equivalent)	Triad CMT-8120 (Similar Substitute)
Manufacturer	Bourns Inc.	Bourns Inc.	Bourns Inc.	Triad Magnetics
Series	8100	8100	8100	CMT
Product Status	Obsolete	Active	Active	Active
Inductance @ Frequency	2.4 mH @ 1 kHz	2.4 mH @ 1 kHz	1 mH @ 1 kHz	2.4 mH @ 1 kHz
Number of Lines	2	2	2	2
Current Rating (Max)	17A	17A	20A	17A
DC Resistance (DCR) (Max)	8mOhm	8mOhm	7mOhm	8mOhm
Operating Temperature	-55°C ~ 105°C	-55°C ~ 105°C	-55°C ~ 105°C	-55°C ~ 105°C
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole
Size / Dimension	1.700" L × 0.900" W (43.18mm × 22.86mm)	1.700" L × 0.900" W (43.18mm × 22.86mm)	1.700" L × 0.900" W (43.18mm × 22.86mm)	1.700" L × 0.900" W (43.18mm × 22.86mm)
Height (Max)	1.650" (41.91mm)	1.650" (41.91mm)	1.650" (41.91mm)	1.650" (41.91mm)
RoHS Status	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Voltage Rating - AC	Not specified	Not specified	Not specified	1500V (1.5kV)
Approval Agency	Not specified	Not specified	Not specified	CSA, IEC, UL, VDE

Engineering Selection Recommendations

For Direct Replacement: The Bourns 8120-RC is the primary substitute for the obsolete 8120. It provides identical electrical and mechanical specifications while offering active product status and ROHS3 compliance. This part is suitable for designs requiring no circuit modifications.

For Applications Accepting Parameter Variation: The Bourns 8121-RC accommodates designs where reduced inductance (1 mH vs. 2.4 mH) and increased current capacity (20A vs. 17A) are compatible with system requirements. Lower DCR (7mOhm vs. 8mOhm) provides improved thermal performance.

For Multi-Source Qualification: The Triad Magnetics CMT-8120 provides electrical equivalence to the original 8120 with the added benefit of international certifications (CSA, IEC, UL, VDE) and specified AC voltage rating (1500V). This option is applicable for designs requiring multi-source component qualification or enhanced regulatory documentation.

Frequently Asked Questions (FAQ)

Q: Can the 8120-RC be used as a direct drop-in replacement for the obsolete 8120?

A: Yes. The 8120-RC maintains identical inductance (2.4 mH @ 1 kHz), current rating (17A), DC resistance (8mOhm), physical dimensions, and mounting configuration. No circuit modifications are required.

Q: What are the key differences between the 8120-RC and 8121-RC?

A: The 8121-RC has lower inductance (1 mH vs. 2.4 mH), higher current rating (20A vs. 17A), and lower DCR (7mOhm vs. 8mOhm). Physical dimensions and mounting type remain identical. Selection depends on whether the application can tolerate reduced inductance in exchange for higher current capacity.

Q: Is the CMT-8120 from Triad Magnetics electrically equivalent to the Bourns 8120?

A: Yes. The CMT-8120 matches the Bourns 8120 in inductance, current rating, and DCR. It differs in manufacturer and includes additional certifications (CSA, IEC, UL, VDE) and an AC voltage rating specification (1500V).

Q: Are all substitute parts RoHS compliant?

A: The 8120-RC and 8121-RC are ROHS3 compliant. The CMT-8120 is also ROHS3 compliant. The original 8120 is RoHS non-compliant.

Q: Do the substitute parts fit the same PCB footprint?

A: Yes. All substitute parts maintain the same physical dimensions (1.700" L × 0.900" W, 43.18mm × 22.86mm) and height (1.650", 41.91mm) with vertical 4-pin through-hole mounting, ensuring identical PCB compatibility.

Q: Which substitute should be selected for new designs?

A: For electrical equivalence with active product status, select the Bourns 8120-RC. For applications requiring higher current capacity with acceptable inductance reduction, select the Bourns 8121-RC. For multi-source qualification or enhanced regulatory certifications, select the Triad Magnetics CMT-8120.

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