BUL742CFP Equivalent & Substitute Parts

Part Overview

The BUL742CFP is an NPN bipolar junction transistor manufactured by STMicroelectronics, rated for 400 V collector-emitter breakdown voltage and 4 A maximum collector current in a TO-220-3 Full Pack through-hole package. This device is classified as obsolete, necessitating identification of active equivalent components for new designs and ongoing production requirements. Substitute parts must maintain electrical and mechanical compatibility within the specified parameter ranges.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	400	V
Current - Collector (Ic) (Max)	4	A
Power - Max	30	W
Vce Saturation (Max)	1.5	V @ 1A, 3.5A
DC Current Gain (hFE) (Min)	48	@ 100mA, 5V
Current - Collector Cutoff (Max)	250	µA
Operating Temperature (Max)	150	°C (TJ)
Mounting Type	Through Hole	—
Package / Case	TO-220-3 Full Pack	—
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitution of the BUL742CFP is determined by the following critical electrical and mechanical parameters:

Electrical Compatibility Criteria:

Transistor type must be NPN
Voltage - Collector Emitter Breakdown rating must equal or exceed 400 V
Current - Collector (Ic) maximum rating must equal or exceed 4 A
Power dissipation rating must equal or exceed 30 W
Package and mounting type must be TO-220-3 Full Pack through-hole configuration

Regulatory Compliance:

RoHS3 compliance required
REACH Unaffected status required

The MJF18004G from onsemi satisfies all substitution criteria with enhanced electrical ratings (450 V breakdown voltage, 5 A collector current, 35 W power rating) and active product status, making it a direct functional equivalent for the obsolete BUL742CFP.

Parameter Comparison

Parameter	BUL742CFP (STMicroelectronics)	MJF18004G (onsemi)	Unit
Transistor Type	NPN	NPN	—
Voltage - Collector Emitter Breakdown (Max)	400	450	V
Current - Collector (Ic) (Max)	4	5	A
Power - Max	30	35	W
Vce Saturation (Max)	1.5 @ 1A, 3.5A	0.75 @ 0.5A, 2.5A	V
Current - Collector Cutoff (Max)	250	100	µA
DC Current Gain (hFE) (Min)	48 @ 100mA, 5V	14 @ 300mA, 5V	—
Operating Temperature (Max)	150	150	°C (TJ)
Mounting Type	Through Hole	Through Hole	—
Package / Case	TO-220-3 Full Pack	TO-220-3 Full Pack	—
Product Status	Obsolete	Active	—
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	—
REACH Status	REACH Unaffected	REACH Unaffected	—

Engineering Selection Recommendations

The MJF18004G is the qualified substitute for the BUL742CFP based on the following factors:

Product Status: The BUL742CFP is obsolete, while the MJF18004G maintains active product status with current manufacturing availability (2100 pcs in stock versus 1148 pcs for the obsolete part).

Electrical Ratings: The MJF18004G exceeds all minimum electrical requirements of the BUL742CFP. The 450 V breakdown voltage provides 50 V margin above the 400 V requirement, and the 5 A collector current rating exceeds the 4 A specification. The 35 W power rating provides 5 W additional headroom compared to the 30 W BUL742CFP rating.

Regulatory Compliance: Both components are ROHS3 compliant and REACH unaffected, meeting current environmental and regulatory standards.

Package Compatibility: Both devices utilize identical TO-220-3 Full Pack through-hole packaging, ensuring mechanical and thermal interface compatibility without PCB redesign.

Saturation Characteristics: The MJF18004G exhibits lower Vce saturation (0.75 V versus 1.5 V), resulting in reduced power dissipation during switching operation.

Frequently Asked Questions (FAQ)

Q: Can the MJF18004G directly replace the BUL742CFP without circuit modification?

A: Yes. The MJF18004G meets or exceeds all electrical specifications of the BUL742CFP and uses identical TO-220-3 Full Pack packaging. No PCB layout changes are required for mechanical compatibility.

Q: What are the key differences between these two transistors?

A: The MJF18004G provides higher voltage (450 V vs. 400 V), higher current (5 A vs. 4 A), and higher power rating (35 W vs. 30 W). The MJF18004G has lower saturation voltage (0.75 V vs. 1.5 V) and lower collector cutoff current (100 µA vs. 250 µA). The MJF18004G is an active product, while the BUL742CFP is obsolete.

Q: Are there thermal management differences between these parts?

A: Both devices are rated to 150°C maximum junction temperature and use the same TO-220-3 package. Thermal performance depends on PCB layout, heatsinking, and application current levels. The MJF18004G's lower saturation voltage may reduce thermal load in switching applications.

Q: What is the significance of the different DC current gain (hFE) specifications?

A: The BUL742CFP specifies hFE minimum of 48 at 100 mA and 5 V, while the MJF18004G specifies hFE minimum of 14 at 300 mA and 5 V. These measurements occur at different operating points. The MJF18004G's lower hFE at higher current does not prevent substitution; circuit design must account for the actual operating point and required base drive current.

Q: Is the MJF18004G suitable for high-frequency switching applications?

A: The MJF18004G is specified with 13 MHz transition frequency and is part of the onsemi SWITCHMODE™ series, indicating suitability for switching applications. The BUL742CFP does not specify transition frequency. Application suitability depends on specific circuit requirements and switching frequency.

Q: What packaging format is the MJF18004G supplied in?

A: The MJF18004G is supplied in tube packaging, while the BUL742CFP packaging format is not specified in the available data. Both use identical TO-220-3 Full Pack component packaging for circuit board mounting.

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