FMMT449TC Equivalent & Substitute Parts

Part Overview

The FMMT449TC is an NPN bipolar junction transistor manufactured by Diodes Incorporated, designed for general-purpose switching and amplification applications. This device features a 30 V collector-emitter breakdown voltage, 1 A maximum collector current, and 500 mW power dissipation in a surface mount SOT-23-3 package. The FMMT449TC is classified as obsolete, necessitating identification of active equivalent and substitute components for new designs and production continuity.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Collector Current (Max)	1	A
Collector-Emitter Breakdown Voltage (Max)	30	V
Power Dissipation (Max)	500	mW
Transition Frequency	150	MHz
DC Current Gain (hFE Min)	100	@ 500 mA, 2 V
Operating Temperature Range	−55 to +150	°C
Package	SOT-23-3	—
Mounting Type	Surface Mount	—

Substitute Part Grouping Explanation

Substitution of the FMMT449TC is determined by strict adherence to the following electrical and mechanical parameters:

Primary Substitution Criteria:

Transistor type: NPN
Collector-emitter breakdown voltage: 30 V (minimum)
Collector current rating: ≥1 A
Power dissipation: ≥500 mW
Package: SOT-23-3 (TO-236-3, SC-59)
Mounting type: Surface Mount
Operating temperature range: −55°C to +150°C (minimum)

Parametric Equivalent Classification: Parts meeting all primary criteria with identical electrical performance specifications are classified as parametric equivalents. The FMMT449TA from Diodes Incorporated is a parametric equivalent, differing only in packaging format (Tape & Reel versus cut tape) and product status (Active versus Obsolete).

Manufacturer Recommended Substitutes: Parts exceeding the primary criteria in specific parameters (higher current rating, higher power dissipation, higher transition frequency, or higher DC current gain) are classified as manufacturer recommended substitutes. These parts are electrically compatible and functionally superior in their respective parameter categories.

Current-Limited Substitutes: Parts with reduced maximum collector current (100 mA versus 1 A) are listed for applications where the full 1 A rating is not required. These substitutes maintain voltage and package compatibility but operate within reduced current envelopes.

Parameter Comparison

Part Number	Manufacturer	Ic (Max)	VCEO (Max)	Power (Max)	fT	hFE (Min)	Temp Range	Status	Package
FMMT449TC	Diodes Inc.	1 A	30 V	500 mW	150 MHz	100	−55 to +150°C	Obsolete	SOT-23-3
FMMT449TA	Diodes Inc.	1 A	30 V	500 mW	150 MHz	100	−55 to +150°C	Active	SOT-23-3
2SD2657KT146	Rohm Semi.	1.5 A	30 V	200 mW	330 MHz	270	−55 to +150°C	Active	SOT-23-3
BC848ALT1G	onsemi	100 mA	30 V	300 mW	100 MHz	110	−55 to +150°C	Active	SOT-23-3
BC848B,215	Nexperia	100 mA	30 V	250 mW	100 MHz	200	−55 to +150°C	Active	SOT-23-3
BC848B,235	Nexperia	100 mA	30 V	250 mW	100 MHz	200	−55 to +150°C	Active	SOT-23-3
BC848BE6327HTSA1	Infineon	100 mA	30 V	330 mW	250 MHz	200	−55 to +150°C	Last Time Buy	SOT-23-3
BC848BLT1G	onsemi	100 mA	30 V	300 mW	100 MHz	200	−55 to +150°C	Active	SOT-23-3
BC848CLT1G	onsemi	100 mA	30 V	300 mW	100 MHz	420	−55 to +150°C	Active	SOT-23-3
BC849B,215	Nexperia	100 mA	30 V	250 mW	100 MHz	200	−55 to +150°C	Active	SOT-23-3
BC849BLT1G	onsemi	100 mA	30 V	300 mW	100 MHz	200	−55 to +150°C	Active	SOT-23-3

Engineering Selection Recommendations

Parametric Equivalent (Direct Replacement): The FMMT449TA is the direct parametric equivalent to the FMMT449TC. Both devices share identical electrical specifications and package format. The FMMT449TA is currently in active production status, making it the primary recommendation for applications requiring exact performance matching. The only distinction is packaging format (Tape & Reel for FMMT449TA versus cut tape for FMMT449TC).

Higher Current Rating Substitute: The 2SD2657KT146 from Rohm Semiconductor is suitable for applications where the 1 A collector current rating of the FMMT449TC is insufficient. This device provides 1.5 A maximum collector current while maintaining the 30 V breakdown voltage specification. The 2SD2657KT146 exhibits higher transition frequency (330 MHz) and higher DC current gain (270 minimum), making it appropriate for higher-speed switching applications. Power dissipation is reduced to 200 mW, which may be a limiting factor in high-power applications.

Current-Limited Substitutes (100 mA Devices): The BC848 and BC849 series devices from onsemi and Nexperia are suitable for applications where collector current does not exceed 100 mA. These devices maintain the 30 V breakdown voltage and SOT-23-3 package compatibility. Multiple variants exist within this series, differentiated by DC current gain specifications and product status. All listed BC848 and BC849 variants are in active production status.

Automotive-Qualified Alternatives: The BC848B,215 and BC849B,215 variants from Nexperia carry AEC-Q101 automotive qualification. These parts are suitable for automotive and industrial applications requiring formal qualification documentation.

Last Time Buy Consideration: The BC848BE6327HTSA1 from Infineon is classified as Last Time Buy status. While currently available, this device should not be selected for new designs requiring long-term supply continuity.

Frequently Asked Questions (FAQ)

Q: Can the FMMT449TA be used as a direct replacement for the FMMT449TC?

A: Yes. The FMMT449TA is a parametric equivalent with identical electrical specifications. The only difference is packaging format (Tape & Reel versus cut tape). Both devices are NPN transistors rated for 1 A collector current, 30 V breakdown voltage, and 500 mW power dissipation in SOT-23-3 packages.

Q: What is the primary limitation when substituting BC848 or BC849 series devices for the FMMT449TC?

A: The BC848 and BC849 series devices are rated for maximum collector current of 100 mA, compared to 1 A for the FMMT449TC. These substitutes are suitable only for applications where collector current does not exceed 100 mA. All other electrical parameters (voltage, package, temperature range) remain compatible.

Q: Is the 2SD2657KT146 a suitable substitute for high-current applications?

A: The 2SD2657KT146 provides 1.5 A maximum collector current, exceeding the FMMT449TC specification of 1 A. However, power dissipation is reduced to 200 mW compared to 500 mW for the FMMT449TC. Applications requiring sustained high-current operation at elevated power levels should evaluate thermal management requirements carefully.

Q: Are all substitute parts available in the same SOT-23-3 package?

A: Yes. All listed substitute parts are housed in SOT-23-3 (TO-236-3, SC-59) surface mount packages, ensuring mechanical and footprint compatibility with the FMMT449TC.

Q: What is the significance of product status (Active, Obsolete, Last Time Buy)?

A: Product status indicates supply continuity and manufacturer support. Active status indicates ongoing production and long-term availability. Obsolete status indicates end-of-life with no further production. Last Time Buy status indicates final production run with limited availability. For new designs, selection of Active status components is recommended.

Q: Can BC848 and BC849 devices be used interchangeably?

A: BC848 and BC849 devices share identical electrical specifications and package format. The primary distinction is DC current gain specification. BC848 variants specify minimum hFE of 110 to 420 depending on grade, while BC849 variants specify minimum hFE of 200. Both are suitable for general-purpose switching applications where the specified gain meets circuit requirements.

Q: What is the operating temperature range for all listed substitutes?

A: All listed substitute parts operate across the temperature range of −55°C to +150°C (junction temperature), matching the FMMT449TC specification. This ensures thermal compatibility across industrial and extended temperature applications.

Q: Are there differences in saturation voltage between the FMMT449TC and substitute parts?

A: Yes. The FMMT449TC specifies Vce saturation of 1 V at 200 mA, 2 A. The BC848 and BC849 series specify Vce saturation of 600 mV at 5 mA, 100 mA. The 2SD2657KT146 specifies Vce saturation of 350 mV at 50 mA, 1 A. Applications sensitive to saturation voltage should evaluate these differences against circuit requirements.

Q: Which substitute part offers the highest transition frequency?

A: The 2SD2657KT146 provides transition frequency of 330 MHz, compared to 150 MHz for the FMMT449TC. The BC848BE6327HTSA1 provides 250 MHz. Higher transition frequency enables faster switching operation in high-frequency applications.

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