BFS505,115 RF Transistor NPN Equivalent & Substitute Parts

Part Overview

The BFS505,115 is an RF transistor NPN manufactured by NXP USA Inc., designed for high-frequency applications up to 9GHz. This device operates at 15V collector-emitter breakdown voltage with a maximum power dissipation of 150mW and is housed in a surface mount SC-70 (SOT-323-3) package. The BFS505,115 is classified as obsolete, making identification of equivalent and substitute parts essential for design continuity and procurement planning. Active alternatives with comparable or enhanced electrical characteristics are available from multiple manufacturers.

Substiute Parts

BFS505,115

NXP USA Inc.In Stock: 1210BFS505,115 Datasheet

Current PartRFQ

BFU520WX

NXP USA Inc.In Stock: 3270BFU520WX Datasheet

MFR RecommendedRFQ

2SC4915-Y,LF

Toshiba Semiconductor and StorageIn Stock: 8522SC4915-Y,LF Datasheet

MFR RecommendedRFQ

BFQ19SH6327XTSA1

Infineon TechnologiesIn Stock: 15017BFQ19SH6327XTSA1 Datasheet

MFR RecommendedRFQ

CMPT918 TR PBFREE

Central Semiconductor CorpIn Stock: 1489CMPT918 TR PBFREE Datasheet

MFR RecommendedRFQ

MRF428

MACOM Technology SolutionsIn Stock: 1498MRF428 Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the BFS505,115 is determined by the following critical parameters:

Primary Substitution Criteria:

• Transistor Type: NPN (mandatory match)
• Voltage - Collector Emitter Breakdown (Max): 15V or higher
• Frequency - Transition: 9GHz or higher
• Power - Max: 150mW or higher
• Current - Collector (Ic) (Max): 18mA or higher
• Mounting Type: Surface Mount
• Package compatibility: SC-70 (SOT-323) or equivalent surface mount packages

Secondary Compatibility Factors:

• DC Current Gain (hFE): Minimum 60 @ specified conditions
• Noise Figure: 1.2dB ~ 2.1dB @ 900MHz or better
• Operating Temperature: 175°C or higher
• RoHS3 Compliance and MSL Level 1

The substitute parts listed below meet these criteria with varying degrees of parameter overlap. Each substitute is grouped based on its primary application suitability and electrical performance relative to the BFS505,115.

Parameter Comparison

Engineering Selection Recommendations

BFU520WX (NXP USA Inc.)

The BFU520WX is the closest electrical equivalent to the BFS505,115 within the same manufacturer portfolio. Both devices are housed in SC-70 (SOT-323) surface mount packages and share identical DC current gain specifications. The BFU520WX operates at 10GHz transition frequency, exceeding the BFS505,115 specification of 9GHz. The BFU520WX provides superior noise figure performance at 0.6dB @ 900MHz compared to the BFS505,115 range of 1.2dB ~ 2.1dB. Power dissipation capability is increased to 450mW. The BFU520WX is qualified to AEC-Q101 automotive standards and carries active product status. Voltage rating is reduced to 12V, which may require circuit evaluation if the original design operates near 15V limits. This substitute is suitable for direct replacement in applications where the lower voltage rating is acceptable.

BFQ19SH6327XTSA1 (Infineon Technologies)

The BFQ19SH6327XTSA1 maintains the 15V collector-emitter breakdown voltage specification of the BFS505,115. This device operates at 5.5GHz transition frequency, below the original 9GHz specification. The BFQ19SH6327XTSA1 provides significantly higher power dissipation at 1W and maximum collector current of 120mA. The package is TO-243AA (PG-SOT89), which differs from the SC-70 footprint. This substitute is applicable to applications where frequency requirements are lower than 9GHz and higher power handling is beneficial. PCB layout modifications are required due to package change.

2SC4915-Y,LF (Toshiba Semiconductor and Storage)

The 2SC4915-Y,LF operates at 550MHz transition frequency, significantly below the BFS505,115 specification of 9GHz. This device is suitable only for lower-frequency RF applications. The voltage rating is increased to 30V, and the package is SC-75 (SOT-416), requiring PCB layout changes. This substitute is not recommended for applications requiring 9GHz operation.

CMPT918 TR PBFREE (Central Semiconductor Corp)

The CMPT918 TR PBFREE operates at 600MHz transition frequency, below the BFS505,115 specification of 9GHz. The device is housed in SOT-23 package, differing from the SC-70 footprint. This substitute is applicable only to lower-frequency applications and requires PCB layout modifications.

MRF428 (MACOM Technology Solutions)

The MRF428 is a high-power RF transistor with 150W power dissipation and 20A maximum collector current. This device is mounted in a chassis mount 211-11 package, fundamentally different from the surface mount SC-70 package of the BFS505,115. The MRF428 is suitable for high-power RF amplifier applications and is not a direct substitute for the BFS505,115 in surface mount circuit designs.

Frequently Asked Questions (FAQ)

Q1: Can the BFU520WX directly replace the BFS505,115 on the same PCB?

A: Yes, the BFU520WX can be directly replaced on the same PCB. Both devices use identical SC-70 (SOT-323) surface mount packages with the same pin configuration. However, the reduced collector-emitter breakdown voltage (12V vs. 15V) requires circuit evaluation to confirm the design does not operate above 12V under any condition, including transient overvoltage scenarios.

Q2: Why is the BFQ19SH6327XTSA1 listed as a substitute if it operates at only 5.5GHz?

A: The BFQ19SH6327XTSA1 is listed because it meets the core NPN transistor type requirement and maintains the 15V voltage rating. However, the 5.5GHz transition frequency is below the BFS505,115 specification of 9GHz. This substitute is applicable only to applications where the actual operating frequency is below 5.5GHz, even though the original design specification called for 9GHz capability.

Q3: What is the primary limitation of the 2SC4915-Y,LF and CMPT918 TR PBFREE as substitutes?

A: Both devices operate at significantly lower transition frequencies (550MHz and 600MHz respectively) compared to the BFS505,115 (9GHz). These substitutes are suitable only for lower-frequency RF applications. Additionally, both require PCB layout modifications due to different package types (SC-75 and SOT-23 respectively).

Q4: Is the MRF428 suitable for replacing the BFS505,115 in a surface mount design?

A: No. The MRF428 is a chassis mount device in a 211-11 package, fundamentally incompatible with surface mount PCB designs. The MRF428 is intended for high-power RF amplifier applications requiring discrete component mounting on a chassis or heatsink, not for surface mount circuit board integration.

Q5: What compliance certifications should be verified when selecting a substitute?

A: All listed substitutes maintain ROHS3 compliance and MSL Level 1 (Unlimited) moisture sensitivity rating, matching the BFS505,115 specifications. The BFU520WX additionally carries AEC-Q101 automotive qualification. Verify that the selected substitute meets any application-specific compliance requirements beyond RoHS and MSL ratings.

Q6: How do noise figure specifications compare across the substitute options?

A: The BFU520WX provides the best noise figure at 0.6dB @ 900MHz, superior to the BFS505,115 range of 1.2dB ~ 2.1dB @ 900MHz. The 2SC4915-Y,LF specifies 2.3dB ~ 5dB @ 100MHz, and the CMPT918 TR PBFREE specifies 6dB @ 60MHz. Lower noise figure values indicate better performance in low-signal applications. The MRF428 does not specify noise figure, as it is designed for high-power applications where noise figure is not a primary design criterion.

Q7: What is the impact of different DC current gain (hFE) specifications on substitution?

A: The BFS505,115 specifies hFE minimum of 60 @ 5mA, 6V. The BFU520WX matches this specification exactly. The BFQ19SH6327XTSA1 specifies hFE minimum of 70 @ 70mA, 8V, measured at different bias conditions. The 2SC4915-Y,LF specifies hFE minimum of 100 @ 1mA, 6V. The CMPT918 TR PBFREE specifies hFE minimum of 20 @ 3mA, 1V, significantly lower. Differences in hFE specifications reflect different bias point optimization and may affect circuit biasing requirements. Verify that the substitute's hFE characteristics are compatible with the original circuit biasing network.

Q8: Are there package footprint compatibility considerations?

A: Yes. The BFU520WX uses the same SC-70 (SOT-323) package as the BFS505,115 and requires no PCB layout changes. The BFQ19SH6327XTSA1 uses TO-243AA (PG-SOT89) package, the 2SC4915-Y,LF uses SC-75 (SOT-416) package, and the CMPT918 TR PBFREE uses SOT-23 package. The MRF428 uses a 211-11 chassis mount package. Any substitute using a different package requires PCB layout modification and re-qualification of the circuit design.