FMMT614TC NPN Darlington Transistor Equivalent & Substitute Parts

Part Overview

The FMMT614TC is an NPN Darlington bipolar junction transistor manufactured by Diodes Incorporated, designed for surface mount applications in the SOT-23-3 package. This device operates at a maximum collector-emitter voltage of 100 V with a maximum collector current of 500 mA and dissipates up to 500 mW of power. The part is classified as Active product status with full RoHS3 compliance and unlimited moisture sensitivity rating.

Substitute parts become necessary when the primary component experiences supply constraints, extended lead times, or when design requirements permit operation within reduced electrical parameters. The FMMT614TC can be substituted with lower-rated Darlington transistors that maintain compatible package geometry and surface mount characteristics while operating within reduced voltage and current specifications.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN - Darlington	—
Voltage - Collector Emitter Breakdown (Max)	100	V
Current - Collector (Ic) (Max)	500	mA
Power - Max	500	mW
Vce Saturation (Max) @ Ib, Ic	1 V @ 5 mA, 500 mA	—
DC Current Gain (hFE) (Min) @ Ic, Vce	15000 @ 100 mA, 5 V	—
Current - Collector Cutoff (Max)	10	µA
Operating Temperature Range	-55 to 150	°C
Package / Case	SOT-23-3 (TO-236-3, SC-59)	—
Mounting Type	Surface Mount	—
RoHS Status	ROHS3 Compliant	—
Moisture Sensitivity Level (MSL)	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution of the FMMT614TC is determined by the following criteria:

Package Compatibility: All substitute parts must use the SOT-23-3 surface mount package to ensure mechanical and electrical compatibility with existing PCB layouts and reflow soldering processes.

Transistor Type: All substitutes must be NPN Darlington configuration to maintain identical biasing and switching characteristics.

Electrical Parameter Constraints: Substitute parts operate within reduced maximum ratings compared to the FMMT614TC. The primary limiting factors are:

Maximum collector-emitter voltage reduced from 100 V to 30-32 V
Maximum collector current reduced from 500 mA to 300 mA
Maximum power dissipation reduced from 500 mW to 200 mW
DC current gain (hFE) values range from 5000 to 10000, compared to 15000 for the primary part

Compliance Requirements: All substitute parts maintain RoHS3 compliance, unlimited MSL rating, and Active product status, ensuring regulatory and supply chain consistency.

Substitution is valid only when the application circuit operates within the reduced voltage and current specifications of the substitute device. The FMMT614TC cannot be substituted in circuits requiring the full 100 V collector-emitter voltage or 500 mA collector current capability.

Parameter Comparison

Parameter	FMMT614TC (Diodes)	2SD2142KT146 (Rohm)	2SD1383KT146B (Rohm)
Manufacturer	Diodes Incorporated	Rohm Semiconductor	Rohm Semiconductor
Transistor Type	NPN - Darlington	NPN - Darlington	NPN - Darlington
Voltage - Collector Emitter Breakdown (Max)	100 V	30 V	32 V
Current - Collector (Ic) (Max)	500 mA	300 mA	300 mA
Power - Max	500 mW	200 mW	200 mW
Vce Saturation (Max) @ Ib, Ic	1 V @ 5 mA, 500 mA	1.5 V @ 100 µA, 100 mA	1.5 V @ 400 µA, 200 mA
DC Current Gain (hFE) (Min) @ Ic, Vce	15000 @ 100 mA, 5 V	10000 @ 100 mA, 5 V	5000 @ 100 mA, 5 V
Current - Collector Cutoff (Max)	10 µA	100 nA	1 µA
Operating Temperature Range	-55 to 150 °C	—	—
Package / Case	SOT-23-3	SOT-23-3	SOT-23-3
Mounting Type	Surface Mount	Surface Mount	Surface Mount
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)
Product Status	Active	Active	Active

Engineering Selection Recommendations

Primary Substitute: 2SD2142KT146 (Rohm Semiconductor)

The 2SD2142KT146 is the preferred substitute when application requirements permit operation at maximum 30 V collector-emitter voltage and 300 mA collector current. This part offers the highest DC current gain (10000 @ 100 mA, 5 V) among available substitutes, approaching the performance characteristics of the FMMT614TC. The device maintains full RoHS3 compliance, unlimited MSL rating, and Active product status. Rohm Semiconductor maintains consistent supply availability with 19091 pieces in current inventory.

Secondary Substitute: 2SD1383KT146B (Rohm Semiconductor)

The 2SD1383KT146B operates at a maximum 32 V collector-emitter voltage with identical 300 mA collector current rating. This part exhibits lower DC current gain (5000 @ 100 mA, 5 V) and includes transition frequency specification (250 MHz), making it suitable for applications requiring higher-speed switching characteristics. The device maintains full RoHS3 compliance and unlimited MSL rating. Rohm Semiconductor reports 57400 pieces in current inventory, providing superior supply availability.

Both substitute parts are classified as Active products with full regulatory compliance. Selection between the two substitutes depends on circuit requirements for DC current gain and switching frequency specifications. Neither substitute accommodates the full 100 V collector-emitter voltage or 500 mA collector current of the primary FMMT614TC.

Frequently Asked Questions (FAQ)

Q: Can the FMMT614TC be directly replaced with the 2SD2142KT146 or 2SD1383KT146B in any application?

A: No. Substitution is valid only when the application circuit operates within the reduced electrical specifications of the substitute device. The substitute parts are rated for maximum 30-32 V collector-emitter voltage and 300 mA collector current, compared to 100 V and 500 mA for the FMMT614TC. Applications requiring the full voltage or current ratings of the primary part cannot use these substitutes.

Q: Are the package dimensions identical between the FMMT614TC and substitute parts?

A: Yes. All parts use the SOT-23-3 package (also designated TO-236-3 or SC-59), ensuring identical PCB footprint and reflow soldering compatibility. No layout modifications are required for mechanical substitution.

Q: What is the difference in DC current gain between the primary part and substitutes?

A: The FMMT614TC provides minimum DC current gain of 15000 @ 100 mA, 5 V. The 2SD2142KT146 provides 10000, and the 2SD1383KT146B provides 5000 at the same test conditions. Lower current gain may affect base drive requirements in circuits with tight biasing tolerances.

Q: Do all parts maintain the same compliance certifications?

A: Yes. The FMMT614TC, 2SD2142KT146, and 2SD1383KT146B are all RoHS3 compliant with unlimited moisture sensitivity level (MSL 1) and Active product status. No compliance differences exist between the primary and substitute parts.

Q: Which substitute part should be selected for applications requiring higher switching speed?

A: The 2SD1383KT146B includes transition frequency specification of 250 MHz, compared to no frequency specification for the 2SD2142KT146. For applications requiring documented high-speed switching characteristics, the 2SD1383KT146B is the appropriate selection.

Q: What is the impact of reduced Vce saturation voltage on circuit performance?

A: The substitute parts exhibit higher Vce saturation (1.5 V) compared to the FMMT614TC (1 V). This increases voltage drop across the transistor in saturation mode, resulting in higher power dissipation and reduced output voltage swing. Circuit designs with tight voltage margin requirements may require analysis to confirm acceptable performance.

Q: Are there inventory differences between the substitute parts?

A: Yes. The 2SD1383KT146B has 57400 pieces in stock, while the 2SD2142KT146 has 19091 pieces. For applications with extended production runs, the 2SD1383KT146B offers superior supply availability.

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