BUL45 Equivalent & Substitute Parts

Part Overview

The BUL45 is an NPN bipolar junction transistor manufactured by onsemi, rated for 400 V collector-emitter breakdown voltage and 5 A maximum collector current in a TO-220 through-hole package. This device is classified as obsolete, necessitating identification of functionally equivalent alternatives for new designs and ongoing production requirements. The BUL45 operates across a temperature range of -65°C to 150°C and delivers 75 W maximum power dissipation, making it suitable for switching and linear amplification applications in power supply circuits.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	400	V
Current - Collector (Ic) (Max)	5	A
Power - Max	75	W
Frequency - Transition	12	MHz
Operating Temperature	-65 to 150	°C
Mounting Type	Through Hole	—
Package / Case	TO-220-3	—

Substitute Part Grouping Explanation

Substitution of the BUL45 is determined by matching the following critical electrical and mechanical parameters:

Primary Matching Criteria:

Transistor Type: NPN configuration
Voltage - Collector Emitter Breakdown: minimum 400 V
Current - Collector (Ic) (Max): minimum 5 A
Mounting Type: Through Hole
Package / Case: TO-220-3 or compatible TO-220 variant

Secondary Considerations:

Power - Max: minimum 75 W
Operating Temperature: minimum 150°C upper limit
Frequency - Transition: application-dependent

Substitute parts are grouped into two categories:

Category A - Direct Electrical Equivalents (5 A rated current): Parts with identical or higher voltage ratings, matching 5 A current capability, and equivalent or superior power ratings. These include FJP3305H2TU, TSC742CZ C0G, BUL138, BUL38D, and BUL49D.

Category B - Higher Current Capability (8 A and 12 A rated): Parts with 400 V voltage rating but elevated current ratings (FJP13007H2TU at 8 A, FJP13009H2TU at 12 A). These provide design margin for applications requiring higher current handling.

Category C - Lower Current Capability (4 A rated): Parts with 400 V voltage rating but reduced current ratings (FJP3305H1TU, ST13005, BUL742C). These are suitable only for applications where 4 A maximum current is acceptable.

Parameter Comparison

Part Number	Manufacturer	Ic (Max) [A]	Vce Breakdown (Max) [V]	Power (Max) [W]	Frequency - Transition [MHz]	Operating Temp (Max) [°C]	Package	Product Status	RoHS Status
BUL45	onsemi	5	400	75	12	150	TO-220-3	Obsolete	Non-compliant
FJP3305H2TU	onsemi	4	400	75	4	150	TO-220-3	Last Time Buy	ROHS3 Compliant
FJP13007H2TU	onsemi	8	400	80	4	150	TO-220-3	Last Time Buy	ROHS3 Compliant
FJP13009H2TU	onsemi	12	400	100	4	150	TO-220-3	Active	ROHS3 Compliant
FJP3305H1TU	Fairchild Semiconductor	4	400	75	4	150	TO-220-3	Active	Not specified
TSC742CZ C0G	Taiwan Semiconductor Corporation	5	420	70	Not specified	150	TO-220-3	Active	ROHS3 Compliant
BUL138	STMicroelectronics	5	400	80	Not specified	150	TO-220-3	Active	ROHS3 Compliant
BUL38D	STMicroelectronics	5	450	80	Not specified	150	TO-220-3	Active	ROHS3 Compliant
BUL49D	STMicroelectronics	5	450	80	Not specified	150	TO-220-3	Active	ROHS3 Compliant
BUL742C	STMicroelectronics	4	400	70	Not specified	150	TO-220-3	Active	ROHS3 Compliant
ST13005	STMicroelectronics	4	400	75	Not specified	150	TO-220-3	Active	ROHS3 Compliant

Engineering Selection Recommendations

For Direct Replacement (5 A Current Rating):

BUL138 (STMicroelectronics) and BUL38D (STMicroelectronics) are the primary recommended substitutes. Both devices maintain the 5 A collector current rating, operate at 400 V or higher breakdown voltage, and deliver 80 W power dissipation. Both are ROHS3 compliant and carry Active product status, ensuring long-term availability and regulatory compliance. BUL38D provides additional voltage margin at 450 V breakdown rating.

TSC742CZ C0G (Taiwan Semiconductor Corporation) offers equivalent 5 A current capability with 420 V breakdown voltage and Active product status. This device is ROHS3 compliant and suitable for applications requiring higher voltage margin.

For Applications Tolerating Reduced Current (4 A Maximum):

FJP3305H2TU (onsemi) and ST13005 (STMicroelectronics) are suitable where maximum collector current does not exceed 4 A. Both maintain 400 V breakdown voltage and 75 W power rating. FJP3305H2TU carries Last Time Buy status; ST13005 is Active. Both are ROHS3 compliant.

For Applications Requiring Higher Current Capability:

FJP13007H2TU (onsemi) at 8 A and FJP13009H2TU (onsemi) at 12 A provide design margin for applications exceeding 5 A requirements. FJP13009H2TU is Active with ROHS3 compliance and 100 W power rating. FJP13007H2TU carries Last Time Buy status.

Compliance Considerations:

The BUL45 is RoHS non-compliant. All recommended substitutes except FJP3305H1TU are ROHS3 compliant, meeting current regulatory requirements for new designs and production.

Frequently Asked Questions (FAQ)

Q: Can FJP3305H2TU replace BUL45 in all applications?

A: FJP3305H2TU is suitable only for applications where maximum collector current does not exceed 4 A. The BUL45 is rated for 5 A maximum; FJP3305H2TU is rated for 4 A. Both maintain 400 V breakdown voltage and 75 W power dissipation. Verify application current requirements before substitution.

Q: What is the difference between BUL38D and BUL49D?

A: Both devices are rated for 5 A collector current and 450 V breakdown voltage with 80 W power dissipation in TO-220-3 packages. The primary difference is in DC current gain specifications and saturation voltage characteristics. Both are Active, ROHS3 compliant alternatives to BUL45.

Q: Why is FJP13009H2TU rated for 12 A when BUL45 is only 5 A?

A: FJP13009H2TU is a higher-current variant within the same voltage class (400 V). The elevated current rating provides design margin for applications requiring higher current handling. It is suitable for BUL45 replacement in applications operating at or below 5 A, with the advantage of additional current capacity for future design modifications.

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

A: All listed substitute parts are available in TO-220-3 through-hole packages, ensuring mechanical and thermal compatibility with BUL45 footprints. Verify specific supplier device package designations for packaging format confirmation (tube, bulk, or tape).

Q: Which substitute offers the best long-term availability?

A: FJP13009H2TU (onsemi) carries Active product status, indicating ongoing production and long-term availability. BUL138 and BUL38D (STMicroelectronics) are also Active. FJP3305H2TU and FJP13007H2TU carry Last Time Buy status, indicating limited future availability.

Q: Is RoHS compliance required for my application?

A: The BUL45 is RoHS non-compliant. If RoHS compliance is required, select from ROHS3 compliant alternatives: FJP3305H2TU, FJP13007H2TU, FJP13009H2TU, TSC742CZ C0G, BUL138, BUL38D, BUL49D, BUL742C, or ST13005.

Q: Can I use a 4 A rated device in a circuit designed for 5 A?

A: No. Using a 4 A rated device (FJP3305H2TU, FJP3305H1TU, BUL742C, or ST13005) in a circuit requiring 5 A operation exceeds the device rating and creates reliability risk. Select devices rated for 5 A or higher: BUL138, BUL38D, BUL49D, or TSC742CZ C0G.

Q: What is the significance of transition frequency differences?

A: BUL45 specifies 12 MHz transition frequency. Most substitutes specify 4 MHz. Transition frequency affects switching speed in high-frequency applications. For applications operating below 4 MHz, substitutes are suitable. For applications requiring 12 MHz operation, verify substitute device performance in application-specific testing.

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