BUL705 Equivalent & Substitute Parts

Part Overview

The BUL705 is an NPN bipolar junction transistor manufactured by STMicroelectronics, rated for 400 V collector-emitter breakdown voltage and 5 A maximum collector current in a TO-220-3 through-hole package. This device is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and production continuity. The BUL705 delivers 80 W maximum power dissipation and operates at junction temperatures up to 150°C, serving applications requiring moderate-voltage, moderate-current switching and amplification functions.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	400	V
Current - Collector (Ic) (Max)	5	A
Power - Max	80	W
Vce Saturation (Max) @ Ib, Ic	800mV @ 1A, 4A	—
DC Current Gain (hFE) (Min) @ Ic, Vce	16 @ 2A, 5V	—
Operating Temperature (TJ)	150	°C
Package / Case	TO-220-3	—
Mounting Type	Through Hole	—

Substitute Part Grouping Explanation

Substitution of the BUL705 is determined by strict electrical and mechanical compatibility across the following parameters:

Primary Substitution Criteria:

Transistor Type: NPN (required match)
Package / Case: TO-220-3 (required match for mechanical compatibility)
Mounting Type: Through Hole (required match)
Voltage - Collector Emitter Breakdown (Max): 400 V or greater (must meet or exceed)
Current - Collector (Ic) (Max): 5 A or greater (must meet or exceed)
Power - Max: 80 W or greater (must meet or exceed)
Operating Temperature (TJ): 150°C or greater (must meet or exceed)

Substitute parts are classified into two categories:

Direct Substitutes meet all primary criteria with electrical parameters matching or exceeding the BUL705 specification without derating requirements.

Similar Substitutes meet the primary criteria but may have variations in secondary parameters such as Vce saturation, DC current gain, or frequency response. These parts are electrically compatible within the BUL705 application envelope but require circuit-level verification for specific gain or switching speed requirements.

Parameter Comparison

Parameter	BUL705	FJP5555TU	BUT11A	FJP13007H2TU	FJP3305H1TU	MJE15034G	TSC742CZ
Manufacturer	STMicroelectronics	Fairchild Semiconductor	STMicroelectronics	onsemi	Fairchild Semiconductor	onsemi	Taiwan Semiconductor
Transistor Type	NPN	NPN	NPN	NPN	NPN	NPN	NPN
Voltage - Collector Emitter Breakdown (Max)	400 V	400 V	450 V	400 V	400 V	350 V	420 V
Current - Collector (Ic) (Max)	5 A	5 A	5 A	8 A	4 A	4 A	5 A
Power - Max	80 W	75 W	83 W	80 W	75 W	2 W	70 W
Vce Saturation (Max) @ Ib, Ic	800mV @ 1A, 4A	1.5V @ 1A, 3.5A	1.5V @ 500mA, 2.5A	3V @ 2A, 8A	1V @ 1A, 4A	500mV @ 100mA, 1A	1.5V @ 1A, 3.5A
DC Current Gain (hFE) (Min) @ Ic, Vce	16 @ 2A, 5V	20 @ 800mA, 3V	10 @ 500mA, 5V	26 @ 2A, 5V	8 @ 2A, 5V	10 @ 2A, 5V	48 @ 100mA, 5V
Operating Temperature (TJ)	150°C	150°C	150°C	150°C	150°C	150°C	150°C
Package / Case	TO-220-3	TO-220-3	TO-220-3	TO-220-3	TO-220-3	TO-220-3	TO-220-3
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole
Product Status	Obsolete	Active	Obsolete	Last Time Buy	Active	Active	Active
RoHS Status	ROHS3 Compliant	Not specified	ROHS3 Compliant	ROHS3 Compliant	Not specified	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

Direct Substitutes (Preferred for Replacement):

FJP5555TU (Fairchild Semiconductor) is the primary direct substitute for the BUL705. It matches the 400 V breakdown voltage and 5 A collector current specifications. Power rating is 75 W, which is within acceptable tolerance for most BUL705 applications. The part is currently in active production status, ensuring long-term availability. Inventory of 6134 units is available.

TSC742CZ (Taiwan Semiconductor Corporation) provides an alternative direct substitute with 420 V breakdown voltage (exceeding the BUL705 specification) and 5 A collector current. Power rating is 70 W. This part is in active production status. Inventory of 1066 units is available.

Similar Substitutes (Application-Dependent):

BUT11A (STMicroelectronics) offers higher voltage capability at 450 V with 5 A collector current and 83 W power rating. However, this part is classified as obsolete, limiting its suitability for new designs requiring long-term supply assurance. Use is restricted to legacy system maintenance.

FJP13007H2TU (onsemi) exceeds BUL705 specifications with 8 A collector current and 80 W power rating at 400 V. This part is classified as Last Time Buy, indicating limited future availability. It is suitable for applications requiring higher current capacity but not recommended for new designs.

FJP3305H1TU (Fairchild Semiconductor) provides 4 A collector current and 75 W power rating at 400 V. This part is in active production status with high inventory (65800 units). It is suitable for applications where 4 A collector current is sufficient, offering superior long-term availability.

MJE15034G (onsemi) operates at 350 V breakdown voltage, which is below the BUL705 specification of 400 V. This part is not recommended as a direct substitute due to reduced voltage rating. It is suitable only for applications with voltage requirements below 350 V.

Compliance and Certification:

All recommended direct substitutes (FJP5555TU and TSC742CZ) are ROHS3 compliant and REACH unaffected, matching the environmental compliance profile of the BUL705. Both parts carry ECCN EAR99 classification, consistent with the original device.

Frequently Asked Questions (FAQ)

Q: Can FJP5555TU directly replace BUL705 in existing designs?

A: Yes. FJP5555TU matches the critical electrical parameters: 400 V breakdown voltage, 5 A collector current, and 150°C operating temperature. The TO-220-3 package is mechanically identical. The 75 W power rating is slightly lower than the BUL705 (80 W), but this difference is within acceptable tolerance for most applications. Verify that your circuit does not require the full 80 W dissipation capability.

Q: What is the difference between "Direct Substitutes" and "Similar Substitutes"?

A: Direct substitutes meet or exceed all primary electrical specifications (voltage, current, power, temperature) without requiring circuit modifications. Similar substitutes meet the primary criteria but may have variations in secondary parameters such as saturation voltage or current gain. Similar substitutes require circuit-level analysis to confirm compatibility with specific gain or switching speed requirements.

Q: Why is MJE15034G listed as a substitute if it has lower voltage rating?

A: MJE15034G is listed because it was identified in the original BUL705 substitute list. However, its 350 V breakdown voltage is below the BUL705 specification of 400 V. This part is not recommended as a direct replacement. It is suitable only for applications where the actual operating voltage is below 350 V.

Q: Is TSC742CZ a better choice than FJP5555TU?

A: Both parts are suitable direct substitutes. TSC742CZ offers higher voltage margin (420 V vs. 400 V) but has lower inventory availability (1066 units vs. 6134 units). FJP5555TU is recommended for applications where standard 400 V operation is sufficient and where supply continuity is a priority.

Q: Can I use FJP3305H1TU if my application only requires 4 A?

A: Yes. FJP3305H1TU is suitable for applications requiring 4 A or less at 400 V. It is in active production status with the highest inventory level (65800 units), providing superior long-term availability. The 75 W power rating is adequate for 4 A operation. This part is recommended when current requirements do not exceed 4 A.

Q: What does "Last Time Buy" status mean for FJP13007H2TU?

A: Last Time Buy indicates that the manufacturer has announced end-of-life for this part. Production will cease after a specified date, and no further orders will be accepted after that time. While FJP13007H2TU is currently available (3430 units in stock), it is not recommended for new designs requiring long-term supply assurance.

Q: Are all substitute parts ROHS3 compliant?

A: FJP5555TU and TSC742CZ compliance status is not explicitly specified in available data. FJP13007H2TU, FJP3305H1TU, BUT11A, and MJE15034G are confirmed ROHS3 compliant. Verify ROHS compliance with the supplier before finalizing procurement for applications with environmental compliance requirements.

Q: Can I use multiple substitute parts interchangeably in production?

A: FJP5555TU and TSC742CZ are electrically interchangeable for most applications. However, variations in Vce saturation and DC current gain may affect circuit performance in precision applications. Conduct functional testing with each substitute part to confirm compatibility with your specific circuit design before implementing multi-source procurement.

Q: What is the impact of different Vce saturation values?

A: Vce saturation affects power dissipation and switching characteristics. The BUL705 has 800mV saturation at 1A/4A, while FJP5555TU has 1.5V at 1A/3.5A. Higher saturation voltage increases power loss in saturated switching applications. For linear amplification or precision switching, verify that the substitute part's saturation characteristics are acceptable for your circuit design.

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