FMMT3904TA Equivalent & Substitute Parts

Part Overview

The FMMT3904TA is an NPN bipolar junction transistor manufactured by Diodes Incorporated, designed for general-purpose switching and amplification applications. This device operates at 40 V collector-emitter breakdown voltage with a maximum collector current of 200 mA and transition frequency of 300 MHz. The part is classified as obsolete, necessitating identification of active equivalent and substitute components for new designs and ongoing production requirements. Substitute parts must maintain electrical compatibility across critical parameters including voltage rating, current capacity, gain characteristics, and thermal performance.

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	300 mV @ 5 mA, 50 mA	—
DC Current Gain (hFE) (Min) @ Ic, Vce	100 @ 10 mA, 1 V	—
Power - Max	330	mW
Frequency - Transition	300	MHz
Operating Temperature	-55 to 150	°C
Mounting Type	Surface Mount	—
Package / Case	TO-236-3, SC-59, SOT-23-3	—

Substitute Part Grouping Explanation

Substitute parts for the FMMT3904TA are classified into two categories based on electrical and compliance characteristics:

Direct Electrical Equivalents maintain all critical electrical parameters: 40 V collector-emitter breakdown voltage, 200 mA maximum collector current, 300 mV saturation voltage at specified bias conditions, 100 minimum DC current gain, and 300 MHz transition frequency. These parts are functionally interchangeable in applications where the original FMMT3904TA was specified.

Higher-Rated Alternatives exceed one or more electrical parameters while maintaining compatibility with the original application envelope. These parts provide enhanced performance margins in specific areas such as maximum power dissipation, collector current capacity, or collector-emitter breakdown voltage. Selection of higher-rated alternatives is appropriate when design margins or thermal considerations warrant increased component ratings.

All substitute parts listed maintain surface mount packaging in the SOT-23-3 or equivalent form factor, ensuring mechanical compatibility with existing PCB layouts. RoHS3 compliance and unlimited moisture sensitivity level (MSL 1) are standard across active substitute options.

Parameter Comparison

Part Number	Manufacturer	Product Status	Ic (Max) mA	Vce(br) V	Vce Sat mV	hFE (Min)	Power mW	Freq MHz	Temp °C	Package	RoHS
FMMT3904TA	Diodes Incorporated	Obsolete	200	40	300 @ 5mA, 50mA	100 @ 10mA, 1V	330	300	-55 to 150	SOT-23-3	Non-compliant
MMBT3904-7-F	Diodes Incorporated	Active	200	40	300 @ 5mA, 50mA	100 @ 10mA, 1V	300	300	-55 to 150	SOT-23-3	ROHS3
CMPT3904G TR PBFREE	Central Semiconductor Corp	Active	200	40	300 @ 5mA, 50mA	100 @ 10mA, 1V	350	300	-65 to 150	SOT-23-3	ROHS3
MMBT3904LT1G	onsemi	Active	200	40	300 @ 5mA, 50mA	100 @ 10mA, 1V	300	300	-55 to 150	SOT-23-3	ROHS3
MMST3904T146	Rohm Semiconductor	Active	200	40	300 @ 5mA, 50mA	100 @ 10mA, 1V	200	300	-55 to 150	SOT-23-3	ROHS3
SST3904T116	Rohm Semiconductor	Active	200	40	300 @ 5mA, 50mA	100 @ 10mA, 1V	350	300	-55 to 150	SOT-23-3	ROHS3
SMBT3904E6327HTSA1	Infineon Technologies	Last Time Buy	200	40	300 @ 5mA, 50mA	100 @ 10mA, 1V	330	300	-55 to 150	SOT-23-3	ROHS3
BC817-16,215	Nexperia USA Inc.	Active	500	45	700 @ 50mA, 500mA	100 @ 100mA, 1V	250	100	-55 to 150	TO-236AB	ROHS3
BC817-16,235	Nexperia USA Inc.	Active	500	45	700 @ 50mA, 500mA	100 @ 100mA, 1V	250	100	-55 to 150	TO-236AB	ROHS3
BC817-16LT1G	onsemi	Active	500	45	700 @ 50mA, 500mA	100 @ 100mA, 1V	300	100	-65 to 150	SOT-23-3	ROHS3
BC817-16LT3G	onsemi	Active	500	45	700 @ 50mA, 500mA	100 @ 100mA, 1V	300	100	-65 to 150	SOT-23-3	ROHS3

Engineering Selection Recommendations

Direct Electrical Equivalents (Recommended for Drop-In Replacement)

MMBT3904-7-F (Diodes Incorporated), MMBT3904LT1G (onsemi), CMPT3904G TR PBFREE (Central Semiconductor Corp), SMBT3904E6327HTSA1 (Infineon Technologies), MMST3904T146 (Rohm Semiconductor), and SST3904T116 (Rohm Semiconductor) maintain identical electrical specifications to the FMMT3904TA across all critical parameters. These parts are classified as active products with RoHS3 compliance, providing immediate substitution capability for new designs and production continuity.

MMBT3904-7-F carries automotive-grade qualification (AEC-Q101) and is available in high volume (185,200 pieces), making it the primary recommended substitute for applications requiring automotive compliance or extended supply assurance.

MMBT3904LT1G (onsemi) offers the largest available inventory (605,100 pieces) and extended operating temperature range (-65°C to 150°C), providing enhanced thermal margin for demanding applications.

Higher-Rated Alternatives (Application-Dependent Selection)

BC817-16,215, BC817-16,235 (Nexperia USA Inc.), BC817-16LT1G, and BC817-16LT3G (onsemi) provide enhanced electrical ratings: 500 mA maximum collector current (2.5× the original specification), 45 V collector-emitter breakdown voltage (1.125× the original specification), and 250–300 mW power dissipation. These parts are suitable for applications where the original FMMT3904TA operates near maximum ratings or where design margin enhancement is required. The BC817 series exhibits reduced transition frequency (100 MHz versus 300 MHz), limiting applicability to lower-frequency switching circuits.

Product Status Considerations

SMBT3904E6327HTSA1 is classified as Last Time Buy, indicating discontinued production with limited remaining inventory (253,664 pieces). This part is suitable for near-term production requirements but not recommended for long-term design commitments.

All recommended direct equivalents maintain unlimited moisture sensitivity level (MSL 1) and REACH unaffected status, ensuring compliance with standard manufacturing and environmental requirements.

Frequently Asked Questions (FAQ)

Q: Can MMBT3904-7-F directly replace FMMT3904TA in existing designs?

A: Yes. MMBT3904-7-F maintains identical electrical specifications across all critical parameters: 40 V collector-emitter breakdown voltage, 200 mA maximum collector current, 300 mV saturation voltage, 100 minimum DC current gain, and 300 MHz transition frequency. The part is pin-compatible in SOT-23-3 packaging and carries RoHS3 compliance. No circuit modifications are required.

Q: What is the difference between MMBT3904LT1G and MMBT3904-7-F?

A: Both parts are electrically identical with 40 V, 200 mA, and 300 MHz specifications. MMBT3904LT1G (onsemi) offers extended operating temperature range (-65°C to 150°C versus -55°C to 150°C) and significantly higher inventory availability (605,100 versus 185,200 pieces). Selection depends on thermal requirements and supply chain preferences.

Q: Why do BC817 series parts have different electrical ratings?

A: BC817 transistors are designed for higher-current applications with 500 mA maximum collector current and 45 V breakdown voltage, compared to the FMMT3904TA's 200 mA and 40 V ratings. These parts are not direct electrical equivalents but serve as higher-performance alternatives for applications requiring enhanced current capacity or voltage margin. The reduced transition frequency (100 MHz) limits use to lower-frequency circuits.

Q: Are all substitute parts RoHS3 compliant?

A: All active substitute parts listed (MMBT3904-7-F, MMBT3904LT1G, CMPT3904G TR PBFREE, MMST3904T146, SST3904T116, BC817 variants) are RoHS3 compliant. The original FMMT3904TA is RoHS non-compliant, making substitution necessary for applications subject to RoHS requirements.

Q: What packaging options are available for FMMT3904TA substitutes?

A: Direct electrical equivalents are available in SOT-23-3 packaging, maintaining mechanical compatibility with existing PCB layouts. BC817 alternatives are available in TO-236AB and SOT-23-3 variants. All parts maintain the same pin configuration and footprint compatibility within their respective package families.

Q: Is SMBT3904E6327HTSA1 suitable for new production designs?

A: SMBT3904E6327HTSA1 is classified as Last Time Buy with limited remaining inventory (253,664 pieces). This part is suitable for near-term production runs but not recommended for long-term design commitments. Active alternatives such as MMBT3904-7-F or MMBT3904LT1G are preferred for designs with extended production timelines.

Q: What is the significance of the Vce saturation specification?

A: Vce saturation (300 mV @ 5 mA, 50 mA) defines the minimum voltage drop across the transistor in fully saturated switching mode. All listed direct equivalents maintain this specification, ensuring identical switching performance and power dissipation characteristics in digital switching applications.

Q: Can MMST3904T146 be used in high-frequency applications?

A: MMST3904T146 maintains 300 MHz transition frequency, identical to the FMMT3904TA, and is suitable for high-frequency switching applications. However, its maximum power dissipation is reduced to 200 mW (versus 330 mW for the original part), requiring thermal design verification in power-intensive applications.

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