MJE18004 NPN Bipolar Transistor Equivalent & Substitute Parts

Part Overview

The MJE18004 is an NPN bipolar junction transistor manufactured by onsemi, rated for 450 V collector-emitter breakdown voltage and 5 A maximum collector current. Housed in a TO-220-3 through-hole package, this device is part of the SWITCHMODE™ series and is classified as obsolete. The MJE18004 is designed for high-voltage switching applications requiring 75 W power dissipation capability.

Due to its obsolete product status, identifying equivalent and substitute parts is necessary for ongoing design support, production continuity, and component sourcing. Active alternatives with matching or comparable electrical specifications are available from multiple manufacturers.

Substiute Parts

MJE18004

onsemiIn Stock: 4131MJE18004 Datasheet

Current PartRFQ

BUT11A

STMicroelectronicsIn Stock: 2451BUT11A Datasheet

DirectRFQ

MJE18004G

onsemiIn Stock: 1405MJE18004G Datasheet

DirectRFQ

BUL38D

STMicroelectronicsIn Stock: 8764BUL38D Datasheet

DirectRFQ

BUL49D

STMicroelectronicsIn Stock: 6249BUL49D Datasheet

DirectRFQ

TSC742CZ C0G

Taiwan Semiconductor CorporationIn Stock: 1121TSC742CZ C0G Datasheet

DirectRFQ

BUL742C

STMicroelectronicsIn Stock: 25236BUL742C Datasheet

SimilarRFQ

PHD13005,127

WeEn SemiconductorsIn Stock: 6929PHD13005,127 Datasheet

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ST13005

STMicroelectronicsIn Stock: 8499ST13005 Datasheet

SimilarRFQ

STL128D

STMicroelectronicsIn Stock: 3688STL128D Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the MJE18004 is determined by the following critical electrical and mechanical parameters:

Primary Substitution Criteria:

• Transistor Type: NPN
• Voltage - Collector Emitter Breakdown (Max): 450 V or higher
• Current - Collector (Ic) (Max): 5 A or higher
• Package / Case: TO-220-3
• Mounting Type: Through Hole

Secondary Compatibility Factors:

• Power - Max: 75 W or higher
• Vce Saturation characteristics
• DC Current Gain (hFE)
• Operating Temperature Range: minimum 150°C (TJ)

Substitute parts are classified into two categories:

Direct Equivalents: Parts meeting all primary substitution criteria with 450 V breakdown voltage and 5 A collector current rating.

Similar Alternatives: Parts with reduced voltage (400 V) or current (4 A) ratings that maintain functional compatibility in applications where the full 450 V / 5 A specification is not required.

Parameter Comparison

Engineering Selection Recommendations

Direct Replacement (Full Specification Match):

MJE18004G is the primary direct replacement for MJE18004. Both parts are manufactured by onsemi, share identical electrical specifications (450 V, 5 A, 75 W, 13 MHz transition frequency), and are housed in TO-220-3 packages. MJE18004G is currently in active production status with RoHS3 compliance, making it the preferred choice for new designs and production continuity.

Full-Specification Alternatives (450 V / 5 A Rating):

BUL38D and BUL49D, both from STMicroelectronics, meet the complete electrical specification of the MJE18004 with 450 V breakdown voltage and 5 A collector current. Both are active products with RoHS3 compliance. BUL38D offers 80 W power dissipation with lower saturation voltage (1.1 V), while BUL49D provides similar power rating with different saturation characteristics. These parts are suitable for direct substitution in applications requiring the full 450 V / 5 A capability.

BUT11A, manufactured by STMicroelectronics, also meets the 450 V / 5 A specification but carries obsolete product status. This part is not recommended for new designs despite matching electrical parameters.

Reduced-Specification Alternatives (400-420 V / 4-5 A Rating):

TSC742CZ C0G (Taiwan Semiconductor Corporation), BUL742C, PHD13005,127, ST13005, and STL128D are active products with reduced voltage ratings (400-420 V) and/or reduced current ratings (4 A). These parts are suitable for applications where the full 450 V specification is not required. All are RoHS3 compliant and available in TO-220-3 packages.

TSC742CZ C0G maintains 5 A collector current with 420 V breakdown voltage, making it the closest alternative among reduced-specification parts. PHD13005,127 and ST13005 both provide 75 W power dissipation at 400 V / 4 A ratings.

Compliance and Availability:

All recommended active substitutes are RoHS3 compliant and REACH unaffected. MJE18004G, BUL38D, BUL49D, and TSC742CZ C0G are currently in stock with substantial inventory levels, ensuring supply continuity.

Frequently Asked Questions (FAQ)

Q: Can MJE18004G be used as a direct replacement for MJE18004?

A: Yes. MJE18004G is manufactured by onsemi with identical electrical specifications: 450 V breakdown voltage, 5 A collector current, 75 W power dissipation, and 13 MHz transition frequency. Both use TO-220-3 packages. MJE18004G is currently in active production with RoHS3 compliance, whereas MJE18004 is obsolete.

Q: What is the difference between direct equivalents and similar alternatives?

A: Direct equivalents (MJE18004G, BUL38D, BUL49D, BUT11A) maintain the full 450 V / 5 A electrical specification. Similar alternatives (TSC742CZ C0G, BUL742C, PHD13005,127, ST13005, STL128D) have reduced voltage (400-420 V) and/or current (4 A) ratings. Selection depends on application requirements.

Q: Are all substitute parts available in the same TO-220-3 package?

A: Yes. All listed substitute parts use TO-220-3 through-hole packages, ensuring mechanical compatibility with existing PCB layouts and thermal management solutions.

Q: Which substitute part offers the best thermal performance?

A: BUL38D and BUL49D both provide 80 W power dissipation, exceeding the original MJE18004 specification of 75 W. BUL38D exhibits lower saturation voltage (1.1 V) compared to the original part (750 mV), which may result in reduced heat generation in switching applications.

Q: Are there RoHS compliance differences between substitute parts?

A: All active substitute parts listed (MJE18004G, BUL38D, BUL49D, TSC742CZ C0G, BUL742C, PHD13005,127, ST13005, STL128D) are RoHS3 compliant. The original MJE18004 is RoHS non-compliant. BUT11A is also RoHS3 compliant but carries obsolete status.

Q: Can reduced-specification parts (400 V / 4 A) be used in applications designed for 450 V / 5 A?

A: Reduced-specification parts are suitable only if the application does not require the full 450 V breakdown voltage or 5 A collector current. Circuit analysis is required to confirm that operating conditions remain within the reduced part's ratings. These alternatives are not suitable for applications with peak voltage transients or current surges approaching the original specifications.

Q: What is the inventory status of substitute parts?

A: MJE18004G (1,372 pcs), BUL38D (8,725 pcs), BUL49D (6,200 pcs), and TSC742CZ C0G (1,066 pcs) are currently in stock. BUL742C has the highest inventory (25,200 pcs). All parts are available as new original components.

Q: How do saturation voltage differences affect circuit performance?

A: Saturation voltage (Vce Sat) affects power dissipation and switching speed. The original MJE18004 specifies 750 mV at 500 mA / 2.5 A. Substitute parts exhibit varying saturation characteristics: BUL38D (1.1 V), BUL49D (1.2 V), BUT11A (1.5 V), and TSC742CZ C0G (1.5 V). Higher saturation voltage results in increased power loss during saturation. Circuit design must account for these differences in thermal calculations.

Q: Is transition frequency a critical parameter for substitution?

A: The original MJE18004 specifies 13 MHz transition frequency. Most substitute parts do not provide transition frequency specifications. If high-frequency switching performance is critical to the application, MJE18004G is the only substitute with identical 13 MHz specification. Other substitutes may exhibit different switching characteristics.