FMMT451TC Equivalent & Substitute Parts

Part Overview

The FMMT451TC is an NPN bipolar junction transistor manufactured by Diodes Incorporated, designed for general-purpose switching and amplification applications. The device features a 60 V collector-emitter breakdown voltage, 1 A maximum collector current, and 500 mW power dissipation in a surface mount SOT-23-3 package. The FMMT451TC 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 continued availability.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	60	V
Current - Collector (Ic) (Max)	1	A
Power - Max	500	mW
Frequency - Transition	150	MHz
Vce Saturation (Max) @ Ib, Ic	350mV @ 15mA, 150mA	—
DC Current Gain (hFE) (Min) @ Ic, Vce	50 @ 150mA, 10V	—
Operating Temperature Range	-55 to 150	°C
Package / Case	SOT-23-3	—
Mounting Type	Surface Mount	—

Substitute Part Grouping Explanation

Substitute parts are classified into two categories based on electrical parameter compatibility with the FMMT451TC:

Category 1: Parametric Equivalents Parts that maintain identical or equivalent electrical specifications across all critical parameters: 60 V collector-emitter breakdown voltage, 1 A maximum collector current, 500 mW power dissipation, 150 MHz transition frequency, and SOT-23-3 package compatibility. These parts provide direct functional replacement with no circuit redesign required.

Category 2: Functional Substitutes with Parameter Deviations Parts that operate within the same voltage and package class but exhibit differences in one or more electrical parameters. These include variations in maximum collector current (100 mA to 2 A), transition frequency (100 MHz to 200 MHz), saturation voltage, and current gain specifications. Functional substitutes require circuit analysis to confirm compatibility within the specific application context.

Key Parameters Determining Substitution:

Collector-emitter breakdown voltage (VCEO): Must equal or exceed 60 V
Maximum collector current (Ic): Must support application current requirements
Power dissipation (Pmax): Must accommodate thermal load
Transition frequency (fT): Must meet bandwidth requirements
Package type: SOT-23-3 or compatible surface mount package
Saturation voltage (VCE sat): Must satisfy switching performance requirements
DC current gain (hFE): Must provide adequate base drive capability

Parameter Comparison

Part Number	Manufacturer	Product Status	Ic (Max)	VCEO (Max)	Pmax	fT	Package	VCE sat @ Ib, Ic	hFE (Min) @ Ic, Vce
FMMT451TC	Diodes Incorporated	Obsolete	1 A	60 V	500 mW	150 MHz	SOT-23-3	350mV @ 15mA, 150mA	50 @ 150mA, 10V
FMMT451TA	Diodes Incorporated	Active	1 A	60 V	500 mW	150 MHz	SOT-23-3	350mV @ 15mA, 150mA	50 @ 150mA, 10V
2SC5866TLQ	Rohm Semiconductor	Active	2 A	60 V	500 mW	200 MHz	TSMT3	500mV @ 100mA, 1A	120 @ 100mA, 2V
2SC5866TLR	Rohm Semiconductor	Active	2 A	60 V	500 mW	200 MHz	TSMT3	500mV @ 100mA, 1A	120 @ 100mA, 2V
BC846,215	NXP USA Inc.	Active	100 mA	65 V	250 mW	100 MHz	SOT-23-3	400mV @ 5mA, 100mA	110 @ 2mA, 5V
BC846A,215	Nexperia USA Inc.	Active	100 mA	65 V	250 mW	100 MHz	SOT-23-3	400mV @ 5mA, 100mA	110 @ 2mA, 5V
BC846ALT1G	onsemi	Active	100 mA	65 V	300 mW	100 MHz	SOT-23-3	600mV @ 5mA, 100mA	110 @ 2mA, 5V
BC846B,215	Nexperia USA Inc.	Active	100 mA	65 V	250 mW	100 MHz	SOT-23-3	400mV @ 5mA, 100mA	200 @ 2mA, 5V
BC846B,235	Nexperia USA Inc.	Active	100 mA	65 V	250 mW	100 MHz	SOT-23-3	400mV @ 5mA, 100mA	200 @ 2mA, 5V
BC846B-TP	Micro Commercial Co	Active	100 mA	65 V	225 mW	100 MHz	SOT-23-3	500mV @ 5mA, 100mA	200 @ 2mA, 5V
BC846BLT1G	onsemi	Active	100 mA	65 V	300 mW	100 MHz	SOT-23-3	600mV @ 5mA, 100mA	200 @ 2mA, 5V

Engineering Selection Recommendations

Primary Recommendation: FMMT451TA

The FMMT451TA from Diodes Incorporated is the direct parametric equivalent to the obsolete FMMT451TC. This part maintains identical electrical specifications across all critical parameters: 1 A maximum collector current, 60 V collector-emitter breakdown voltage, 500 mW power dissipation, 150 MHz transition frequency, and SOT-23-3 package configuration. The FMMT451TA carries active product status with substantial inventory availability (155,300 pieces), ensuring long-term supply continuity. Both parts share identical RoHS3 compliance, moisture sensitivity level (MSL 1), and REACH unaffected status. This substitution requires no circuit modification and provides complete functional compatibility.

Secondary Recommendations: Rohm 2SC5866 Series

The 2SC5866TLQ and 2SC5866TLR from Rohm Semiconductor offer enhanced electrical performance characteristics while maintaining 60 V collector-emitter breakdown voltage compatibility. These parts feature 2 A maximum collector current (double the FMMT451TC specification), 200 MHz transition frequency (33% higher), and improved DC current gain (120 minimum versus 50 minimum). The TSMT3 package differs from SOT-23-3, requiring PCB layout verification. These parts are suitable for applications requiring higher current capacity or bandwidth performance. Both variants carry active product status and RoHS3 compliance.

Tertiary Recommendations: BC846 Series

The BC846 family from NXP USA Inc., Nexperia USA Inc., onsemi, and Micro Commercial Co provides functional substitution for low-current applications. All BC846 variants operate at 65 V collector-emitter breakdown voltage (5 V margin above FMMT451TC) and feature 100 mA maximum collector current. These parts are suitable only for applications where the FMMT451TC operates below 100 mA collector current. The BC846 series exhibits lower power dissipation (225 to 300 mW) and reduced transition frequency (100 MHz) compared to the FMMT451TC. All BC846 variants maintain SOT-23-3 package compatibility and active product status with RoHS3 compliance. Selection among BC846 variants depends on specific hFE and saturation voltage requirements.

Frequently Asked Questions (FAQ)

Q: Can FMMT451TA directly replace FMMT451TC without circuit modification?

A: Yes. The FMMT451TA is a parametric equivalent with identical electrical specifications. No circuit redesign is required. Both parts share the same maximum collector current (1 A), collector-emitter breakdown voltage (60 V), power dissipation (500 mW), transition frequency (150 MHz), saturation voltage characteristics, and current gain specifications. The SOT-23-3 package is identical, enabling direct PCB substitution.

Q: What are the key differences between FMMT451TC and the Rohm 2SC5866 series?

A: The 2SC5866 series provides higher current capacity (2 A versus 1 A), higher transition frequency (200 MHz versus 150 MHz), and higher DC current gain (120 versus 50). The collector-emitter breakdown voltage remains at 60 V. The primary difference is package type: 2SC5866 uses TSMT3 while FMMT451TC uses SOT-23-3. This package difference requires PCB layout verification. The 2SC5866 series is suitable for applications requiring enhanced performance specifications.

Q: Are BC846 variants suitable replacements for FMMT451TC in all applications?

A: No. BC846 variants are limited to applications where collector current does not exceed 100 mA. The FMMT451TC is rated for 1 A maximum collector current. If the application requires collector currents between 100 mA and 1 A, BC846 variants will not provide adequate current capacity. BC846 variants are suitable only for low-signal applications or where the FMMT451TC operates well below its 1 A rating.

Q: What is the significance of the different BC846 variants (A, B, ALT1G, BLT1G)?

A: BC846 variants differ in DC current gain (hFE) specifications and saturation voltage characteristics. BC846A variants specify 110 minimum hFE at 2 mA, 5V. BC846B variants specify 200 minimum hFE at 2 mA, 5V. onsemi variants (ALT1G, BLT1G) feature higher power dissipation (300 mW versus 250 mW) and higher saturation voltage (600 mV versus 400 mW). Selection depends on base drive requirements and switching performance specifications for the specific application.

Q: Can FMMT451TC be used in applications requiring 2 A collector current?

A: No. The FMMT451TC is rated for 1 A maximum collector current. Applications requiring 2 A collector current must use the Rohm 2SC5866 series or equivalent higher-current devices. Operating the FMMT451TC above its 1 A rating will result in device failure.

Q: What packaging considerations apply when substituting with 2SC5866 series?

A: The 2SC5866 series uses TSMT3 package (SC-96) instead of SOT-23-3. TSMT3 is a larger package with different pin spacing and footprint. PCB layout must be verified for physical compatibility. Thermal characteristics may differ due to package geometry. Consult device datasheets for detailed package dimensions and thermal specifications before implementing this substitution.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. All substitute parts listed (FMMT451TA, 2SC5866TLQ, 2SC5866TLR, BC846 series variants) carry RoHS3 compliance certification. All parts are REACH unaffected and carry EAR99 ECCN classification. Compliance status is identical across all recommended substitutes.

Q: What is the moisture sensitivity level (MSL) for substitute parts?

A: All substitute parts carry MSL 1 (Unlimited) classification, identical to the FMMT451TC. This indicates no moisture sensitivity restrictions and unlimited shelf life under standard storage conditions.

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