BD441STU Equivalent & Substitute Parts

Part Overview

The BD441STU is an NPN bipolar junction transistor manufactured by onsemi, rated for 80 V collector-emitter breakdown voltage and 4 A maximum collector current in a TO-126-3 through-hole package. This device is classified as obsolete, making identification of equivalent and substitute parts essential for ongoing design support and production continuity. The BD441STU delivers 36 W maximum power dissipation with a 3 MHz transition frequency, suitable for general-purpose switching and amplification applications requiring moderate current handling.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	80	V
Current - Collector (Ic) (Max)	4	A
Power - Max	36	W
Frequency - Transition	3	MHz
DC Current Gain (hFE) (Min) @ Ic, Vce	40 @ 500mA, 1V	—
Vce Saturation (Max) @ Ib, Ic	800mV @ 200mA, 2A	—
Current - Collector Cutoff (Max)	100	µA
Operating Temperature (TJ)	150	°C
Mounting Type	Through Hole	—
Package / Case	TO-126-3	—

Substitute Part Grouping Explanation

Substitution of the BD441STU is determined by strict equivalence across the following critical parameters:

Direct Equivalence Criteria:

Transistor type (NPN)
Voltage rating (80 V minimum collector-emitter breakdown)
Current rating (4 A minimum collector current)
Power dissipation (36 W minimum)
Transition frequency (3 MHz minimum)
Through-hole mounting configuration
TO-126 package family compatibility

Substitution Categories:

Direct Substitute (Electrical & Mechanical Equivalence): BD441G meets all electrical specifications of the BD441STU with identical voltage, current, and power ratings. Both devices share the same base product number (BD441) and are housed in compatible TO-126 packages. The BD441G is currently in active production status, providing long-term availability compared to the obsolete BD441STU.

Similar Substitute (Reduced Current Rating): 2N4923G shares the same voltage rating (80 V), transition frequency (3 MHz), and through-hole TO-126 package configuration. However, the 2N4923G is rated for 1 A maximum collector current and 30 W maximum power dissipation, representing a reduced current capability. This device is suitable only for applications where the 4 A current requirement of the BD441STU can be reduced to 1 A or lower.

Parameter Comparison

Parameter	BD441STU (Main)	BD441G (Direct)	2N4923G (Similar)
Manufacturer	onsemi	onsemi	onsemi
Product Status	Obsolete	Active	Active
Transistor Type	NPN	NPN	NPN
Voltage - Collector Emitter Breakdown (Max)	80 V	80 V	80 V
Current - Collector (Ic) (Max)	4 A	4 A	1 A
Power - Max	36 W	36 W	30 W
Frequency - Transition	3 MHz	3 MHz	3 MHz
DC Current Gain (hFE) (Min) @ Ic, Vce	40 @ 500mA, 1V	40 @ 500mA, 1V	30 @ 500mA, 1V
Vce Saturation (Max) @ Ib, Ic	800mV @ 200mA, 2A	800mV @ 300mA, 3A	600mV @ 100mA, 1A
Current - Collector Cutoff (Max)	100 µA	100 µA	500 µA
Operating Temperature (TJ)	150°C	-55°C ~ 150°C	-65°C ~ 150°C
Mounting Type	Through Hole	Through Hole	Through Hole
Package / Case	TO-126-3	TO-126	TO-126
RoHS Status	Not specified	ROHS3 Compliant	ROHS3 Compliant
REACH Status	REACH Unaffected	REACH Unaffected	REACH Unaffected

Engineering Selection Recommendations

For Direct Replacement: BD441G is the primary substitute for BD441STU applications. Both devices share identical electrical specifications across voltage, current, and power parameters. The BD441G is currently in active production with ROHS3 compliance certification, providing regulatory alignment for new designs and production continuity. The BD441G is suitable for all applications currently using the BD441STU without circuit modification.

For Current-Limited Applications: 2N4923G serves as an alternative where circuit design permits reduction of maximum collector current from 4 A to 1 A. This device maintains the 80 V voltage rating and 3 MHz transition frequency. The 2N4923G is active in production with ROHS3 compliance. Selection of 2N4923G requires circuit analysis to confirm that peak and sustained current demands do not exceed 1 A.

Compliance Considerations: Both substitute parts carry REACH Unaffected status, matching the regulatory profile of the BD441STU. The BD441G and 2N4923G both achieve ROHS3 compliance, supporting environmental and regulatory requirements for modern manufacturing.

Frequently Asked Questions (FAQ)

Q: Can BD441G be used as a direct replacement for BD441STU in existing designs?

A: Yes. BD441G provides complete electrical and mechanical equivalence to BD441STU. Both devices are rated for 80 V, 4 A, and 36 W with identical DC current gain specifications. The TO-126 package of BD441G is mechanically compatible with TO-126-3 footprints. No circuit modification is required.

Q: What is the primary difference between BD441G and 2N4923G?

A: The maximum collector current rating differs. BD441G is rated for 4 A maximum collector current, while 2N4923G is rated for 1 A maximum collector current. Both share the same 80 V voltage rating and 3 MHz transition frequency. Selection depends on circuit current requirements.

Q: Is 2N4923G suitable for all BD441STU applications?

A: No. 2N4923G is suitable only for applications where the circuit design permits operation at 1 A or lower collector current. If the original design requires sustained or peak currents exceeding 1 A, 2N4923G will not function as a substitute. BD441G must be used for full 4 A capability.

Q: Are there package compatibility concerns when substituting BD441STU?

A: BD441STU uses TO-126-3 packaging. Both BD441G and 2N4923G use TO-126 packaging. These packages are mechanically compatible for through-hole mounting applications. Pin configuration and lead spacing are equivalent.

Q: What is the production status of available substitutes?

A: BD441STU is classified as obsolete. BD441G and 2N4923G are both in active production, ensuring long-term availability and supply chain continuity for new designs and ongoing production requirements.

Q: Do the substitute parts meet current environmental regulations?

A: Yes. Both BD441G and 2N4923G are ROHS3 compliant and carry REACH Unaffected status, matching the regulatory profile of BD441STU and supporting compliance with current environmental standards.

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