MMST3904-7 Equivalent & Substitute Parts

Part Overview

The MMST3904-7 is an NPN bipolar junction transistor manufactured by Diodes Incorporated, designed for general-purpose switching and amplification applications. The device features a 40 V collector-emitter breakdown voltage, 200 mA maximum collector current, and 300 MHz transition frequency in a surface mount SOT-323 package. The MMST3904-7 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 within the specified parameter ranges while offering active product status and improved availability.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Collector-Emitter Breakdown Voltage (Max)	40	V
Collector Current (Max)	200	mA
Power Dissipation (Max)	200	mW
Transition Frequency	300	MHz
DC Current Gain (hFE Min)	100	@ 10mA, 1V
Vce Saturation (Max)	300	mV @ 5mA, 50mA
Operating Temperature Range	-55 to 150	°C
Package Type	SOT-323 (SC-70)	Surface Mount

Substitute Part Grouping Explanation

Substitute parts for the MMST3904-7 are classified into two functional categories based on electrical parameter compatibility:

Category 1: Direct Electrical Equivalents Parts that maintain identical or superior electrical specifications across all critical parameters: collector-emitter breakdown voltage (40 V minimum), collector current (200 mA minimum), power dissipation (200 mW), transition frequency (300 MHz minimum), and DC current gain (100 minimum at specified conditions). These parts are pin-compatible and package-compatible with the original MMST3904-7 in SOT-323 packaging.

Category 2: Functional Substitutes with Parameter Variations Parts that operate within the same application space but feature modified electrical characteristics. These substitutes may exhibit higher collector current ratings, higher breakdown voltages, or different DC current gain specifications. Functional substitutes require circuit-level verification to confirm suitability for the intended application.

Key Parameters Determining Substitution Eligibility:

Collector-Emitter Breakdown Voltage: minimum 40 V
Collector Current: minimum 200 mA
Power Dissipation: 200 mW
Package: SOT-323 surface mount
Mounting Type: Surface mount
Transistor Type: NPN

Parameter Comparison

Part Number	Manufacturer	Product Status	Ic (Max) mA	Vce(br) (Max) V	Vce Sat (Max) mV	hFE (Min)	Freq (MHz)	Power (mW)	Temp Range °C	Package
MMST3904-7	Diodes Incorporated	Obsolete	200	40	300	100	300	200	-55 to 150	SOT-323
MMST3904-7-F	Diodes Incorporated	Active	200	40	300	100	300	200	-55 to 150	SOT-323
MMST3904-TP	Micro Commercial Co	Active	200	40	300	100	300	200	-55 to 150	SOT-323
UMT3904T106	Rohm Semiconductor	Active	200	40	300	100	300	200	-55 to 150	SOT-323
2PC4081R,115	Nexperia USA Inc.	Active	150	50	400	180	100	200	-55 to 150	SOT-323
2PC4081R,135	Nexperia USA Inc.	Active	150	50	400	180	100	200	-55 to 150	SOT-323
BC817-16W,115	NXP USA Inc.	Active	500	45	700	100	100	200	-55 to 150	SOT-323
BC817-16W-TP	Micro Commercial Co	Active	500	45	700	100	100	200	-55 to 150	SOT-323
BC817-25W,115	Nexperia USA Inc.	Active	500	45	700	160	100	200	-55 to 150	SOT-323
BC817-25W,135	Nexperia USA Inc.	Active	500	45	700	160	100	200	-55 to 150	SOT-323
BC817-40W,115	Nexperia USA Inc.	Active	500	45	700	250	100	200	-55 to 150	SOT-323

Engineering Selection Recommendations

Direct Equivalents (Category 1)

MMST3904-7-F, MMST3904-TP, and UMT3904T106 are direct electrical equivalents to the obsolete MMST3904-7. These parts maintain identical collector current (200 mA), collector-emitter breakdown voltage (40 V), power dissipation (200 mW), and transition frequency (300 MHz) specifications. All three parts are in active product status with RoHS3 compliance. MMST3904-7-F is manufactured by Diodes Incorporated, the original manufacturer, and is available in Cut Tape and Digi-Reel packaging with 65,300 units in stock. MMST3904-TP is supplied by Micro Commercial Co with 75,820 units available. UMT3904T106 from Rohm Semiconductor features a UMT3 package variant and has 21,100 units in stock. All three direct equivalents are suitable for one-to-one replacement in existing designs without circuit modification.

Functional Substitutes (Category 2)

The 2PC4081R series (Nexperia USA Inc.) and BC817 series (NXP USA Inc. and Micro Commercial Co) are functional substitutes with modified electrical characteristics. The 2PC4081R variants feature 150 mA collector current (25% reduction from original), 50 V collector-emitter breakdown voltage (25% increase), and 100 MHz transition frequency (67% reduction). These parts carry automotive qualification (AEC-Q101) and are suitable for applications where the reduced collector current and transition frequency are acceptable. The BC817 series offers 500 mA collector current (2.5× increase), 45 V collector-emitter breakdown voltage, and 100 MHz transition frequency. BC817 variants differ in DC current gain specifications: BC817-16W at 100 hFE minimum, BC817-25W at 160 hFE minimum, and BC817-40W at 250 hFE minimum. BC817 parts are suitable for applications requiring higher current handling capability.

Compliance and Availability

All active substitute parts maintain RoHS3 compliance and REACH unaffected status. Moisture sensitivity level is 1 (unlimited) for all parts. Direct equivalents offer superior availability (21,100 to 75,820 units in stock) compared to the obsolete MMST3904-7 (24,200 units). Functional substitutes provide additional inventory depth, with BC817-40W,115 offering 69,677 units and BC817-25W,135 offering 28,216 units.

Frequently Asked Questions (FAQ)

Q: Can MMST3904-7-F be used as a direct replacement for MMST3904-7?

A: Yes. MMST3904-7-F is a direct electrical equivalent manufactured by Diodes Incorporated with identical specifications: 200 mA collector current, 40 V breakdown voltage, 300 MHz transition frequency, and 200 mW power dissipation. The part is in active product status and requires no circuit modification.

Q: What is the difference between MMST3904-TP and UMT3904T106?

A: Both parts are direct electrical equivalents with identical electrical specifications. The primary difference is manufacturer: MMST3904-TP is supplied by Micro Commercial Co, while UMT3904T106 is manufactured by Rohm Semiconductor. UMT3904T106 uses a UMT3 package designation instead of SOT-323, though both are physically compatible SC-70 surface mount packages.

Q: Can BC817-40W,115 replace MMST3904-7 in all applications?

A: BC817-40W,115 is a functional substitute with higher collector current (500 mA versus 200 mA) and lower transition frequency (100 MHz versus 300 MHz). The part is suitable for applications where the increased current capability is beneficial and the reduced frequency response is acceptable. Circuit-level verification is required for frequency-sensitive applications.

Q: Why do 2PC4081R variants have lower collector current than MMST3904-7?

A: The 2PC4081R series is designed for automotive applications with AEC-Q101 qualification. The 150 mA collector current rating is intentional for specific automotive circuit requirements. These parts are suitable only for applications where 150 mA current handling is sufficient.

Q: Are all substitute parts available in the same SOT-323 package?

A: Yes. All substitute parts listed are surface mount devices in SOT-323 (SC-70) packaging. Physical footprint compatibility is maintained across all parts, enabling direct PCB layout reuse.

Q: What is the significance of the hFE (DC current gain) variations in BC817 parts?

A: BC817 variants specify different minimum DC current gain values: BC817-16W at 100 hFE, BC817-25W at 160 hFE, and BC817-40W at 250 hFE. Higher hFE values indicate greater current amplification capability. Selection depends on circuit biasing requirements and desired base current levels.

Q: Do all substitute parts support the full -55°C to 150°C operating temperature range?

A: Yes. All direct equivalents (MMST3904-7-F, MMST3904-TP, UMT3904T106) and functional substitutes (2PC4081R series, BC817 series) support the -55°C to 150°C operating temperature range specified for the original MMST3904-7.

Q: What packaging options are available for substitute parts?

A: Direct equivalents are available in Cut Tape (CT) and Digi-Reel packaging. The 2PC4081R series is supplied in Tape & Reel (TR) format. BC817 variants are available in Bulk and Cut Tape & Digi-Reel formats. All parts maintain SOT-323 surface mount compatibility.

Q: Is RoHS compliance maintained across all substitute parts?

A: Yes. All active substitute parts are RoHS3 compliant. The original MMST3904-7 is RoHS non-compliant, making the transition to RoHS3-compliant substitutes necessary for new designs and production compliance.

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