Bourns 8121 Common Mode Choke - Equivalent & Substitute Parts

Part Overview

The Bourns 8121 is a 1 mH, 20A through-hole common mode choke designed for two-line filtering applications. This component is classified as obsolete, making equivalent substitutes necessary for new designs and ongoing production requirements. The 8121 series provides EMI suppression in power line applications with a compact vertical pin configuration and 7mOhm maximum DC resistance.

Substiute Parts

8121

Bourns Inc.In Stock: 9438121 Datasheet

Current PartRFQ

8121-RC

Bourns Inc.In Stock: 35538121-RC Datasheet

DirectRFQ

CMT-8121

Triad MagneticsIn Stock: 3755CMT-8121 Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution for the Bourns 8121 is determined by strict equivalence across the following critical parameters:

• Inductance value: 1 mH @ 1 kHz
• Number of lines: 2-line configuration
• Current rating: 20A maximum
• DC resistance: 7mOhm maximum
• Mounting type: Through hole
• Physical dimensions: 1.700" L x 0.900" W, 1.650" height maximum
• Package configuration: Vertical, 4 PC pin

Two substitute parts meet these criteria: the Bourns 8121-RC (direct manufacturer variant) and the Triad Magnetics CMT-8121 (cross-manufacturer equivalent). Both maintain identical electrical specifications and mechanical compatibility with the original 8121 design.

Parameter Comparison

Engineering Selection Recommendations

For new designs and production applications, the Bourns 8121-RC is the primary recommended substitute. It maintains complete electrical and mechanical equivalence to the original 8121 while offering active product status and ROHS3 compliance. The 8121-RC is available in bulk packaging with substantial inventory (3448 pcs).

The Triad Magnetics CMT-8121 serves as a secondary cross-manufacturer alternative. It provides identical core electrical specifications and mechanical compatibility. The CMT-8121 offers additional certifications (CSA, IEC, UL, VDE) and specified AC voltage rating (1500V), which may be advantageous in applications requiring formal regulatory documentation. The CMT-8121 is also ROHS3 compliant with active product status.

Selection between the two substitutes depends on supply chain requirements, certification needs, and existing vendor relationships. Both parts are electrically and mechanically interchangeable with the obsolete Bourns 8121.

Frequently Asked Questions (FAQ)

Q: Can the Bourns 8121-RC be used as a direct replacement for the Bourns 8121?

A: Yes. The 8121-RC maintains identical inductance (1 mH @ 1 kHz), current rating (20A), DC resistance (7mOhm), operating temperature range (-55°C ~ 105°C), and physical dimensions (1.700" L x 0.900" W, 1.650" height). The vertical 4-pin through-hole package is identical. The primary difference is product status (active vs. obsolete) and RoHS compliance (ROHS3 vs. non-compliant).

Q: What is the difference between the Bourns 8121-RC and the Triad Magnetics CMT-8121?

A: Both parts are electrically and mechanically equivalent. The CMT-8121 provides additional certifications (CSA, IEC, UL, VDE) and specifies an AC voltage rating of 1500V. The 8121-RC does not specify an AC voltage rating. Both are ROHS3 compliant and active products. Selection depends on certification requirements and supply availability.

Q: Are there any packaging differences between these substitutes?

A: The Bourns 8121 is packaged in standard tape format. The Bourns 8121-RC is available in bulk packaging. The Triad Magnetics CMT-8121 is also available in bulk packaging. All three parts use identical vertical 4-pin through-hole package configuration and physical dimensions.

Q: Why is the original Bourns 8121 obsolete?

A: The Bourns 8121 is classified as obsolete. The Bourns 8121-RC represents the active product line continuation with equivalent specifications and improved compliance status.

Q: Can I use the CMT-8121 in applications requiring specific regulatory certifications?

A: The CMT-8121 carries CSA, IEC, UL, and VDE approvals. If your application requires these specific certifications, the CMT-8121 documentation should be reviewed for compliance with your regulatory requirements. The Bourns 8121-RC does not specify approval agencies.

Q: Are the operating temperature ranges identical across all three parts?

A: Yes. All three parts operate across the identical temperature range of -55°C to 105°C.