BUL804 Equivalent & Substitute Parts

Part Overview

The BUL804 is an NPN bipolar junction transistor manufactured by STMicroelectronics, rated for 450 V collector-emitter breakdown voltage and 4 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 procurement continuity. The BUL804 delivers 70 W maximum power dissipation and operates at junction temperatures up to 150°C, serving applications requiring high-voltage switching and amplification in industrial and consumer electronics.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	450	V
Current - Collector (Ic) (Max)	4	A
Power - Max	70	W
Vce Saturation (Max) @ Ib, Ic	1.2V @ 500mA, 2.5A	—
DC Current Gain (hFE) (Min) @ Ic, Vce	10 @ 2A, 5V	—
Operating Temperature (TJ)	150	°C
Package / Case	TO-220-3	—
Mounting Type	Through Hole	—
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitution of the BUL804 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): 450 V or higher (equal or superior rating)
Current - Collector (Ic) (Max): 4 A or higher (equal or superior rating)
Power - Max: 70 W or higher (equal or superior rating)
Operating Temperature (TJ): 150°C or higher (equal or superior rating)

Secondary Compatibility Factors:

RoHS3 Compliance (environmental and regulatory alignment)
Vce Saturation characteristics (switching performance)
DC Current Gain (hFE) (amplification capability)

Substitute parts are grouped into two categories: direct equivalents (matching all primary criteria exactly) and functional substitutes (meeting or exceeding all primary criteria with potential variations in secondary parameters).

Parameter Comparison

Part Number	Manufacturer	Ic (Max) [A]	Vce Breakdown (Max) [V]	Power (Max) [W]	Vce Sat (Max) [V]	hFE (Min)	Package	Product Status
BUL804	STMicroelectronics	4	450	70	1.2 @ 500mA, 2.5A	10 @ 2A, 5V	TO-220-3	Obsolete
BUL1102E	STMicroelectronics	4	450	70	1.5 @ 400mA, 2A	12 @ 2A, 5V	TO-220-3	Active
BUT11A	STMicroelectronics	5	450	83	1.5 @ 500mA, 2.5A	10 @ 500mA, 5V	TO-220-3	Obsolete
FJP3305H2TU	onsemi	4	400	75	1 @ 1A, 4A	26 @ 1A, 5V	TO-220-3	Last Time Buy
FJP5555TU	Fairchild Semiconductor	5	400	75	1.5 @ 1A, 3.5A	20 @ 800mA, 3V	TO-220-3	Active
KSC5338D	onsemi	5	450	75	0.5 @ 200mA, 1A	6 @ 2A, 1V	TO-220-3	Active
TSC742CZ C0G	Taiwan Semiconductor Corporation	5	420	70	1.5 @ 1A, 3.5A	48 @ 100mA, 5V	TO-220-3	Active

Engineering Selection Recommendations

Direct Equivalent (Recommended Primary Substitute):

BUL1102E is the preferred substitute for BUL804. Both devices share identical electrical ratings (4 A, 450 V, 70 W) and package configuration (TO-220-3). BUL1102E is currently in active product status with 16,990 pieces in stock, ensuring long-term availability. Both parts are ROHS3 compliant and carry identical regulatory certifications (REACH Unaffected, EAR99). The BUL1102E exhibits marginally superior DC current gain (12 vs. 10 @ 2A, 5V) and lower collector cutoff current (100µA vs. 250µA), providing enhanced performance characteristics within the same form factor and thermal envelope.

Secondary Substitutes (Higher Current Rating):

BUT11A, FJP5555TU, KSC5338D, and TSC742CZ C0G exceed the BUL804 specifications in collector current (5 A vs. 4 A) and power dissipation (75–83 W vs. 70 W). These devices are suitable for applications where increased current capacity provides design margin. BUT11A is obsolete; FJP5555TU and KSC5338D are active; TSC742CZ C0G is active. All maintain 450 V or higher breakdown voltage ratings and TO-220-3 packaging.

Voltage-Reduced Substitute (Lower Voltage Applications):

FJP3305H2TU operates at 400 V breakdown voltage, 50 V below the BUL804 specification. This device is suitable only for applications where the circuit voltage does not exceed 400 V. FJP3305H2TU is in Last Time Buy status and should not be selected for new designs requiring long-term supply continuity.

Compliance and Regulatory Alignment:

All recommended substitutes maintain ROHS3 compliance and REACH Unaffected status, ensuring compatibility with environmental and regulatory requirements applicable to the BUL804.

Frequently Asked Questions (FAQ)

Q: Can BUL1102E directly replace BUL804 in existing designs?

A: Yes. BUL1102E is a direct electrical and mechanical equivalent. Both devices feature identical maximum ratings (4 A, 450 V, 70 W), operate at 150°C junction temperature, and use the TO-220-3 package. The BUL1102E is currently in active production status, whereas BUL804 is obsolete.

Q: What is the difference between BUL804 and BUT11A?

A: BUT11A provides higher current capacity (5 A vs. 4 A) and greater power dissipation (83 W vs. 70 W) while maintaining the same 450 V breakdown voltage and TO-220-3 package. BUT11A is suitable for applications requiring additional current margin. However, BUT11A is also obsolete; BUL1102E is the recommended active substitute.

Q: Can FJP3305H2TU replace BUL804?

A: FJP3305H2TU is not recommended as a direct replacement. Although it matches the 4 A collector current and TO-220-3 package, its 400 V breakdown voltage is 50 V lower than the BUL804 specification. Use FJP3305H2TU only in applications where circuit voltage does not exceed 400 V. Additionally, FJP3305H2TU is in Last Time Buy status.

Q: Why do some substitutes have higher current ratings than BUL804?

A: Substitutes with 5 A ratings (BUT11A, FJP5555TU, KSC5338D, TSC742CZ C0G) provide design margin and flexibility for applications requiring increased current capacity. These devices are backward-compatible with BUL804 designs operating at 4 A or below, as they exceed all primary electrical specifications.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. All substitute parts listed in this reference are ROHS3 compliant and carry REACH Unaffected status, matching the environmental and regulatory compliance of the BUL804.

Q: What is the significance of product status (Active, Obsolete, Last Time Buy)?

A: Product status indicates supply continuity. Active parts are in current production with ongoing availability. Obsolete parts have reached end-of-life and are available only from existing inventory. Last Time Buy parts are approaching obsolescence and should not be selected for new designs. BUL1102E (Active) is the recommended substitute for long-term design support.

Q: Can I use KSC5338D as a substitute if my application requires 450 V operation?

A: Yes. KSC5338D is rated for 450 V breakdown voltage, matching the BUL804 specification exactly. KSC5338D provides 5 A collector current (exceeding the 4 A requirement) and is currently in active production status. The TO-220-3 package ensures mechanical compatibility.

Q: How do Vce saturation characteristics affect substitution?

A: Vce saturation determines switching speed and power loss in saturated operation. BUL804 exhibits 1.2 V saturation at 500mA base current and 2.5 A collector current. Substitutes show variations in saturation voltage and test conditions. Lower saturation voltage (such as KSC5338D at 0.5 V) indicates faster switching and reduced power dissipation in saturated switching applications. Verify saturation characteristics against circuit requirements.

Q: Is TSC742CZ C0G suitable for high-reliability applications?

A: TSC742CZ C0G is active and ROHS3 compliant. However, its Moisture Sensitivity Level (MSL) is rated at 3 (168 Hours), compared to MSL 1 (Unlimited) for BUL804 and BUL1102E. This indicates greater sensitivity to moisture exposure during storage and handling. For high-reliability applications requiring unlimited moisture tolerance, BUL1102E is the preferred choice.

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