BUX10 Equivalent & Substitute Parts

Part Overview

The BUX10 is an NPN bipolar junction transistor manufactured by STMicroelectronics, housed in a TO-3 chassis mount package. This device is rated for 125 V collector-emitter breakdown voltage, 25 A maximum collector current, and 150 W maximum power dissipation. The BUX10 is classified as obsolete, necessitating identification of equivalent and substitute components for ongoing design support and procurement requirements. Active alternatives with comparable electrical and mechanical characteristics are available from alternative manufacturers.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	125	V
Current - Collector (Ic) (Max)	25	A
Power - Max	150	W
Frequency - Transition	8	MHz
Vce Saturation (Max) @ Ib, Ic	1.2V @ 2A, 20A	V
DC Current Gain (hFE) (Min) @ Ic, Vce	20 @ 10A, 2V	—
Operating Temperature (Max)	200	°C
Package / Case	TO-204AA, TO-3	—
Mounting Type	Chassis Mount	—

Substitute Part Grouping Explanation

Substitute parts for the BUX10 are categorized based on electrical parameter compatibility and product status. Substitution is determined by alignment across the following critical parameters:

Electrical Compatibility Criteria:

Transistor type (NPN)
Collector-emitter breakdown voltage rating (minimum 125 V)
Maximum collector current (minimum 25 A)
Maximum power dissipation (minimum 150 W)
Package compatibility (TO-3 or TO-204AA)

Substitution Categories:

Parametric Equivalent: Parts with identical or superior electrical ratings across all critical parameters and matching package specifications. The BUX10 from NTE Electronics, Inc. meets this classification with matching voltage, current, power, and frequency specifications.

Functional Substitute: Parts with comparable electrical performance within acceptable operating ranges but with variations in secondary parameters such as transition frequency or saturation voltage. The MJ15001G from onsemi qualifies as a functional substitute with higher voltage rating (140 V) and power rating (200 W), though maximum collector current is reduced to 15 A.

Parameter Comparison

Parameter	BUX10 (STMicroelectronics)	BUX10 (NTE Electronics, Inc)	MJ15001G (onsemi)
Transistor Type	NPN	NPN	NPN
Voltage - Collector Emitter Breakdown (Max)	125 V	125 V	140 V
Current - Collector (Ic) (Max)	25 A	25 A	15 A
Power - Max	150 W	150 W	200 W
Frequency - Transition	8 MHz	8 MHz	2 MHz
Vce Saturation (Max) @ Ib, Ic	1.2V @ 2A, 20A	1.2V @ 2A, 20A	1V @ 400mA, 4A
DC Current Gain (hFE) (Min) @ Ic, Vce	20 @ 10A, 2V	20 @ 10A, 2V	25 @ 4A, 2V
Operating Temperature (Max)	200°C	200°C	200°C
Package / Case	TO-204AA, TO-3	TO-204AA, TO-3	TO-204AA, TO-3
Mounting Type	Chassis Mount	Chassis Mount	Through Hole
Product Status	Obsolete	Active	Active
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

Primary Recommendation: BUX10 (NTE Electronics, Inc)

The NTE Electronics BUX10 is the preferred substitute for the obsolete STMicroelectronics BUX10. This part maintains identical electrical specifications across all critical parameters: 125 V breakdown voltage, 25 A maximum collector current, 150 W power dissipation, and 8 MHz transition frequency. Both devices share matching saturation voltage and DC current gain characteristics. The NTE part carries active product status and ROHS3 compliance, ensuring long-term availability and regulatory alignment. Packaging is TO-3 with chassis mount configuration, maintaining mechanical compatibility with existing designs.

Secondary Recommendation: MJ15001G (onsemi)

The MJ15001G serves as a functional substitute for applications where the reduced maximum collector current (15 A versus 25 A) is acceptable. This device provides superior voltage rating (140 V) and power dissipation capability (200 W), offering design margin in high-voltage applications. The MJ15001G is active product status with ROHS3 compliance. The transition frequency is reduced to 2 MHz, which may impact performance in high-frequency switching applications. Mounting type is through-hole rather than chassis mount, requiring mechanical design consideration. This substitute is suitable for lower-current, higher-voltage applications within the same TO-3 package family.

Frequently Asked Questions (FAQ)

Q: Can the BUX10 from NTE Electronics directly replace the obsolete STMicroelectronics BUX10?

A: Yes. The NTE Electronics BUX10 is a parametric equivalent with identical electrical ratings and package specifications. No circuit modifications are required for direct substitution in existing designs.

Q: What are the limitations of using the MJ15001G as a substitute?

A: The MJ15001G has a maximum collector current rating of 15 A compared to the BUX10's 25 A. Applications requiring sustained currents above 15 A cannot use this substitute. Additionally, the transition frequency is 2 MHz versus 8 MHz, limiting use in higher-frequency switching circuits. The mounting type is through-hole, which may require mechanical redesign if the original design uses chassis mount configuration.

Q: Are all substitute parts RoHS compliant?

A: Yes. Both the NTE Electronics BUX10 and onsemi MJ15001G are ROHS3 compliant, matching the compliance status of the original STMicroelectronics BUX10.

Q: What is the difference between chassis mount and through-hole mounting?

A: Chassis mount (BUX10 variants) uses a threaded stud for direct mounting to a heat sink or chassis. Through-hole (MJ15001G) requires insertion into a PCB or mounting bracket with fasteners. The mechanical interface differs, potentially requiring design changes if substituting between these mounting types.

Q: Can the MJ15001G be used in all applications designed for the BUX10?

A: The MJ15001G is suitable only for applications where collector current does not exceed 15 A and transition frequency requirements do not exceed 2 MHz. High-current or high-frequency applications must use the NTE Electronics BUX10 equivalent.

Q: What is the operating temperature range for these devices?

A: All three devices (STMicroelectronics BUX10, NTE Electronics BUX10, and MJ15001G) support maximum junction temperatures of 200°C. The MJ15001G specifies an operating temperature range of −65°C to 200°C.

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