2N4401G Equivalent & Substitute Parts

Part Overview

The 2N4401G is an NPN bipolar junction transistor manufactured by onsemi, rated for 40 V collector-emitter breakdown voltage and 600 mA maximum collector current. This device is packaged in a through-hole TO-92 configuration and is currently listed as obsolete. Due to its obsolete status, equivalent and substitute parts are necessary for ongoing design support, production continuity, and component sourcing. Suitable alternatives maintain the core electrical specifications while offering active product status and improved availability.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	40	V
Current - Collector (Ic) (Max)	600	mA
Power - Max	625	mW
Frequency - Transition	250	MHz
DC Current Gain (hFE) (Min) @ Ic, Vce	100 @ 150mA, 1V	—
Vce Saturation (Max) @ Ib, Ic	750mV @ 50mA, 500mA	—
Operating Temperature Range	-55 to 150	°C
Mounting Type	Through Hole	—
Package / Case	TO-92-3 (TO-226)	—

Substitute Part Grouping Explanation

Substitution of the 2N4401G is determined by strict adherence to the following electrical and mechanical parameters:

Critical Matching Parameters:

Transistor Type: NPN
Voltage - Collector Emitter Breakdown (Max): 40 V minimum
Current - Collector (Ic) (Max): 600 mA minimum
Power - Max: 625 mW minimum
DC Current Gain (hFE) (Min): 100 or greater
Operating Temperature Range: -55°C to 150°C minimum
Mounting Type: Through Hole
Package / Case: TO-92-3 compatible

Allowable Variations:

Frequency - Transition: 250 MHz or higher
Vce Saturation: Values within specified test conditions
Product Status: Active preferred for ongoing availability
Compliance: RoHS3 and REACH compliance preferred

Substitute parts are grouped into two categories: direct equivalents (identical electrical specifications and through-hole packaging) and functional alternatives (enhanced specifications or different packaging with equivalent electrical performance).

Parameter Comparison

Parameter	2N4401G (Main)	2N4401BU	2N4401TF	KSP2222ABU	MMBT4401LT1G	2N4424 PBFREE
Manufacturer	onsemi	onsemi	Fairchild Semiconductor	Fairchild Semiconductor	onsemi	Central Semiconductor Corp
Product Status	Obsolete	Active	Active	Active	Active	Active
Transistor Type	NPN	NPN	NPN	NPN	NPN	NPN
Voltage - Collector Emitter Breakdown (Max)	40 V	40 V	40 V	40 V	40 V	40 V
Current - Collector (Ic) (Max)	600 mA	600 mA	600 mA	600 mA	600 mA	500 mA
Power - Max	625 mW	625 mW	625 mW	625 mW	300 mW	625 mW
Frequency - Transition	250 MHz	250 MHz	250 MHz	300 MHz	250 MHz	—
DC Current Gain (hFE) (Min) @ Ic, Vce	100 @ 150mA, 1V	100 @ 150mA, 1V	100 @ 150mA, 1V	100 @ 150mA, 10V	100 @ 150mA, 1V	180 @ 2mA, 4.5V
Vce Saturation (Max) @ Ib, Ic	750mV @ 50mA, 500mA	750mV @ 50mA, 500mA	750mV @ 50mA, 500mA	1V @ 50mA, 500mA	750mV @ 50mA, 500mA	300mV @ 3mA, 50mA
Operating Temperature Range	-55 to 150°C	-55 to 150°C	-55 to 150°C	to 150°C	-55 to 150°C	-65 to 150°C
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole	Surface Mount	Through Hole
Package / Case	TO-92-3	TO-92-3	TO-92-3	TO-92-3	SOT-23-3	TO-92-3
RoHS Status	—	ROHS3 Compliant	—	—	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

Direct Equivalents (Recommended for Pin-Compatible Replacement):

2N4401BU (onsemi) is the primary direct equivalent. This part maintains identical electrical specifications to the 2N4401G, including 40 V breakdown voltage, 600 mA collector current, 625 mW power dissipation, and 250 MHz transition frequency. The 2N4401BU is active in production status with RoHS3 compliance, ensuring long-term availability and regulatory alignment. Through-hole TO-92-3 packaging provides direct mechanical compatibility. This part is suitable for direct substitution in existing designs without circuit modification.

2N4401TF (Fairchild Semiconductor) provides identical electrical specifications and through-hole TO-92-3 packaging. This part is active in production and offers an alternative source for the 2N4401 base product number. Formed leads variant is available. This part is suitable for applications requiring dual-source qualification.

Enhanced Specification Alternatives (Through-Hole):

KSP2222ABU (Fairchild Semiconductor) exceeds the 2N4401G specifications with 300 MHz transition frequency (versus 250 MHz) while maintaining 40 V breakdown voltage and 600 mA collector current. This part is active in production. The higher transition frequency provides performance margin for high-frequency applications. Vce saturation is specified at 1V (versus 750mV), which may affect switching speed in saturation-mode circuits. Through-hole TO-92-3 packaging is compatible.

2N4424 PBFREE (Central Semiconductor Corp) is rated for 500 mA collector current (versus 600 mA) and maintains 40 V breakdown voltage and 625 mW power dissipation. This part is active in production with RoHS3 compliance. Operating temperature range extends to -65°C (versus -55°C), providing enhanced low-temperature performance. DC current gain is specified at 180 (versus 100), offering higher amplification. This part is suitable for applications where the 500 mA current rating is sufficient and higher gain is beneficial. Through-hole TO-92-3 packaging is compatible.

Surface Mount Alternative:

MMBT4401LT1G (onsemi) provides equivalent electrical specifications in a surface-mount SOT-23-3 package. Power dissipation is reduced to 300 mW (versus 625 mW) due to smaller package thermal characteristics. This part is active in production with RoHS3 compliance and unlimited moisture sensitivity level. This part is suitable for new designs utilizing surface-mount assembly or space-constrained applications. Direct pin-for-pin replacement with through-hole designs is not possible without adapter circuitry.

Frequently Asked Questions (FAQ)

Q: Can 2N4401BU be used as a direct replacement for 2N4401G?

A: Yes. The 2N4401BU maintains identical electrical specifications (40 V, 600 mA, 625 mW, 250 MHz) and through-hole TO-92-3 packaging. The primary difference is product status: 2N4401BU is active in production while 2N4401G is obsolete. No circuit modification is required.

Q: What is the difference between 2N4401BU and KSP2222ABU?

A: Both parts are rated for 40 V and 600 mA. KSP2222ABU offers higher transition frequency (300 MHz versus 250 MHz) and higher DC current gain (100 minimum). Vce saturation differs: KSP2222ABU is specified at 1V versus 750mV for 2N4401BU. The higher saturation voltage may result in slower switching in saturation-mode applications. Both use through-hole TO-92-3 packaging.

Q: Is MMBT4401LT1G compatible with through-hole designs?

A: No. MMBT4401LT1G uses surface-mount SOT-23-3 packaging, while the 2N4401G uses through-hole TO-92-3 packaging. MMBT4401LT1G is suitable for new surface-mount designs only. Adapter circuitry or PCB redesign is required for through-hole board integration.

Q: Can 2N4424 PBFREE be used in all 2N4401G applications?

A: 2N4424 PBFREE is suitable for most applications but has a lower maximum collector current rating (500 mA versus 600 mA). Applications requiring the full 600 mA rating must use 2N4401BU, 2N4401TF, or KSP2222ABU. The 2N4424 PBFREE offers higher DC current gain (180 versus 100) and extended low-temperature operation (-65°C versus -55°C).

Q: What compliance certifications are important for substitute selection?

A: RoHS3 compliance is critical for new designs and production environments subject to European Union regulations. 2N4401BU, MMBT4401LT1G, and 2N4424 PBFREE are RoHS3 compliant. All listed substitutes are REACH unaffected. Compliance status should be verified against specific application and regional requirements.

Q: Are there inventory considerations when selecting a substitute?

A: Yes. Inventory levels vary significantly: MMBT4401LT1G has the highest inventory (605,300 pcs), followed by KSP2222ABU (70,087 pcs). 2N4401BU has 9,900 pcs available. 2N4424 PBFREE has 8,327 pcs. Inventory levels should be confirmed with suppliers for production planning and long-term availability assurance.

Q: What is the thermal difference between through-hole and surface-mount packages?

A: MMBT4401LT1G (SOT-23-3 surface mount) is rated for 300 mW maximum power dissipation, while through-hole alternatives (2N4401BU, 2N4401TF, KSP2222ABU, 2N4424 PBFREE) are rated for 625 mW. The smaller surface-mount package has reduced thermal mass and heat dissipation capability. Thermal design and power budget must account for this difference in surface-mount applications.

Q: Can KSP2222ABU be used in low-frequency applications designed for 2N4401G?

A: Yes. KSP2222ABU is suitable for low-frequency applications. The higher transition frequency (300 MHz) provides performance margin without degradation in low-frequency operation. However, the higher Vce saturation (1V versus 750mV) may affect switching characteristics in saturation-mode circuits. Circuit performance should be verified if saturation-mode switching speed is critical.

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