MMBT3904K Equivalent & Substitute Parts

Part Overview

The MMBT3904K is an NPN bipolar junction transistor manufactured by onsemi, housed in a SOT-23-3 surface mount package. This device is rated for 40 V collector-emitter breakdown voltage, 200 mA maximum collector current, and 350 mW power dissipation. The part is currently listed as obsolete, necessitating identification of active equivalent and substitute components for ongoing design and production requirements. Equivalent parts maintain identical electrical and mechanical specifications, while substitute parts offer compatible performance within defined parameter tolerances.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	40	V
Current - Collector (Ic) (Max)	200	mA
Vce Saturation (Max) @ Ib, Ic	300mV @ 5mA, 50mA	—
DC Current Gain (hFE) (Min) @ Ic, Vce	100 @ 10mA, 1V	—
Power - Max	350	mW
Frequency - Transition	300	MHz
Operating Temperature	-55 to 150	°C
Mounting Type	Surface Mount	—
Package / Case	SOT-23-3 (TO-236-3, SC-59)	—

Substitute Part Grouping Explanation

Substitute parts are classified into two categories based on electrical parameter alignment with the MMBT3904K:

Direct Equivalents maintain all critical electrical specifications: 40 V breakdown voltage, 200 mA maximum collector current, 300 MHz transition frequency, 100 mA minimum DC current gain at 10 mA and 1 V, and SOT-23-3 package compatibility. These parts differ only in product status (active versus obsolete) and manufacturing compliance certifications (RoHS3, AEC-Q101 automotive qualification where applicable).

Similar Alternatives share the same package and NPN configuration but deviate in one or more electrical parameters. These parts are suitable only when circuit design permits relaxed specifications for collector current, breakdown voltage, transition frequency, or power dissipation.

Key parameters determining substitution eligibility:

Transistor Type (NPN)
Voltage - Collector Emitter Breakdown (40 V minimum)
Current - Collector (200 mA minimum)
DC Current Gain (hFE) (100 minimum @ 10mA, 1V)
Frequency - Transition (300 MHz minimum)
Package / Case (SOT-23-3)

Parameter Comparison

Part Number	Manufacturer	Product Status	Ic (Max) mA	Vce(br) V	Vce Sat @ Ib, Ic	hFE (Min) @ Ic, Vce	Power mW	Freq MHz	Temp °C	Package	RoHS	Automotive
MMBT3904K	onsemi	Obsolete	200	40	300mV @ 5mA, 50mA	100 @ 10mA, 1V	350	300	-55 to 150	SOT-23-3	—	—
BSR17A	onsemi	Active	200	40	300mV @ 5mA, 50mA	100 @ 10mA, 1V	350	300	-55 to 150	SOT-23-3	ROHS3	—
MMBT3904LT1G	onsemi	Active	200	40	300mV @ 5mA, 50mA	100 @ 10mA, 1V	300	300	-55 to 150	SOT-23-3	ROHS3	—
MMBT3904LT3G	onsemi	Active	200	40	300mV @ 5mA, 50mA	100 @ 10mA, 1V	300	300	-55 to 150	SOT-23-3	ROHS3	—
SMMBT3904LT1G	onsemi	Active	200	40	300mV @ 5mA, 50mA	100 @ 10mA, 1V	300	300	-55 to 150	SOT-23-3	ROHS3	AEC-Q101
SMMBT3904LT3G	onsemi	Active	200	40	300mV @ 5mA, 50mA	100 @ 10mA, 1V	300	300	-55 to 150	SOT-23-3	ROHS3	AEC-Q101
CMPT3904E TR PBFREE	Central Semiconductor Corp	Active	200	40	200mV @ 5mA, 50mA	100 @ 10mA, 1V	350	300	-65 to 150	SOT-23-3	ROHS3	—
CMPT3904G TR PBFREE	Central Semiconductor Corp	Active	200	40	300mV @ 5mA, 50mA	100 @ 10mA, 1V	350	300	-65 to 150	SOT-23-3	ROHS3	—
MMBT3904,215	Nexperia USA Inc.	Active	200	40	300mV @ 5mA, 50mA	100 @ 10mA, 1V	250	300	-55 to 150	SOT-23-3	ROHS3	AEC-Q101
MMBT6429LT1G	onsemi	Active	200	45	600mV @ 5mA, 100mA	500 @ 100µA, 5V	225	700	-55 to 150	SOT-23-3	ROHS3	—
SMMBT4401LT1G	onsemi	Active	600	40	750mV @ 50mA, 500mA	100 @ 150mA, 1V	300	250	-55 to 150	SOT-23-3	ROHS3	—

Engineering Selection Recommendations

Direct Equivalents (Recommended Primary Choices)

BSR17A, MMBT3904LT1G, MMBT3904LT3G, SMMBT3904LT1G, SMMBT3904LT3G, CMPT3904G TR PBFREE, and MMBT3904,215 are direct electrical equivalents to the MMBT3904K. All maintain identical collector current (200 mA), breakdown voltage (40 V), transition frequency (300 MHz), and DC current gain specifications. These parts are active products with RoHS3 compliance.

For automotive applications requiring AEC-Q101 qualification, select SMMBT3904LT1G, SMMBT3904LT3G, or MMBT3904,215. These parts satisfy automotive-grade requirements while maintaining full electrical equivalence.

For general industrial applications without automotive requirements, BSR17A, MMBT3904LT1G, MMBT3904LT3G, or CMPT3904G TR PBFREE provide equivalent performance with active product status and RoHS3 compliance.

CMPT3904E TR PBFREE offers equivalent specifications with extended lower operating temperature limit (-65°C versus -55°C), suitable for applications requiring enhanced cold-temperature performance.

Similar Alternatives (Application-Dependent Selection)

MMBT6429LT1G shares the SOT-23-3 package and NPN configuration but features higher breakdown voltage (45 V), higher transition frequency (700 MHz), and significantly higher DC current gain (500 @ 100µA, 5V). This part is suitable only when circuit design permits or requires these enhanced specifications.

SMMBT4401LT1G provides three times the maximum collector current (600 mA versus 200 mA) while maintaining 40 V breakdown voltage and SOT-23-3 package. This part is suitable for applications requiring higher current handling within the same package footprint.

Frequently Asked Questions (FAQ)

Q: Can MMBT3904LT1G directly replace MMBT3904K in existing designs?

A: Yes. MMBT3904LT1G maintains identical electrical specifications for collector current (200 mA), breakdown voltage (40 V), transition frequency (300 MHz), and DC current gain (100 @ 10mA, 1V). The primary difference is product status (active versus obsolete) and RoHS3 compliance certification. No circuit modifications are required.

Q: What is the difference between MMBT3904LT1G and SMMBT3904LT1G?

A: Both parts are electrically identical. SMMBT3904LT1G carries AEC-Q101 automotive qualification and is designated for automotive-grade applications. Select SMMBT3904LT1G for automotive designs; use MMBT3904LT1G for general industrial applications.

Q: Why does CMPT3904E TR PBFREE show lower Vce saturation (200mV) compared to MMBT3904K (300mV)?

A: Lower saturation voltage indicates improved switching performance and reduced power dissipation during saturation. This is a beneficial characteristic and does not prevent substitution. CMPT3904E TR PBFREE is a direct equivalent with enhanced saturation characteristics.

Q: Can MMBT6429LT1G replace MMBT3904K?

A: MMBT6429LT1G is not a direct equivalent. While it shares the SOT-23-3 package and NPN configuration, it features higher breakdown voltage (45 V), higher transition frequency (700 MHz), and significantly different DC current gain characteristics (500 @ 100µA, 5V versus 100 @ 10mA, 1V). Substitution is possible only if circuit design permits these parameter differences.

Q: Can SMMBT4401LT1G replace MMBT3904K?

A: SMMBT4401LT1G is not a direct equivalent. It provides three times the maximum collector current (600 mA versus 200 mA) and different saturation voltage characteristics. Substitution is possible only in applications where higher current capability is required or beneficial.

Q: Are all listed parts RoHS3 compliant?

A: All active substitute parts listed are RoHS3 compliant. The original MMBT3904K does not specify RoHS status. All recommended replacements meet current environmental compliance requirements.

Q: What is the significance of the packaging designation "Cut Tape (CT) & Digi-Reel®" versus "Tape & Reel (TR)"?

A: Both designations refer to surface mount packaging formats. Cut Tape allows individual component selection; Digi-Reel and Tape & Reel formats provide components on continuous reels for automated assembly. Electrical specifications remain identical regardless of packaging format. Select based on procurement and assembly requirements.

Q: Does MMBT3904,215 from Nexperia differ from onsemi equivalents?

A: MMBT3904,215 is electrically equivalent to MMBT3904K with identical collector current, breakdown voltage, transition frequency, and DC current gain. It is manufactured by Nexperia USA Inc. rather than onsemi and carries AEC-Q101 automotive qualification. Power rating is 250 mW versus 350 mW for the original part, which is acceptable for most applications.

Q: Can I use CMPT3904E TR PBFREE in place of CMPT3904G TR PBFREE?

A: Both parts are electrically equivalent with identical collector current, breakdown voltage, transition frequency, and DC current gain. CMPT3904E shows lower Vce saturation (200mV versus 300mV), indicating superior switching performance. Either part is suitable; CMPT3904E TR PBFREE is preferred for applications sensitive to saturation losses.

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