FMMT491AQTC Equivalent & Substitute Parts

Part Overview

The FMMT491AQTC is an NPN bipolar junction transistor (BJT) manufactured by Diodes Incorporated, designed for mid-performance switching and amplification applications. This surface mount device is packaged in SOT-23-3 and operates across an industrial temperature range of -55°C to 150°C. The part is actively produced, AEC-Q101 qualified for automotive applications, and ROHS3 compliant. Substitute parts are identified when equivalent electrical and mechanical parameters are maintained across the same product family, ensuring direct interchangeability in circuit designs without performance degradation.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Current - Collector (Ic) Max	1	A
Voltage - Collector Emitter Breakdown (Max)	40	V
Vce Saturation (Max) @ Ib, Ic	500mV @ 100mA, 1A	—
Current - Collector Cutoff (Max)	100	nA
DC Current Gain (hFE) Min @ Ic, Vce	300 @ 500mA, 5V	—
Power - Max	500	mW
Frequency - Transition	150	MHz
Operating Temperature Range	-55 to 150	°C
Package / Case	SOT-23-3	—
Mounting Type	Surface Mount	—
Grade	Automotive	—
Qualification	AEC-Q101	—
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitute parts for the FMMT491AQTC are identified within the FMMT491 product family from Diodes Incorporated. Substitution is valid when all of the following parameters remain identical:

Transistor Type: NPN
Maximum Collector Current (Ic): 1 A
Collector Emitter Breakdown Voltage: 40 V
Vce Saturation: 500mV @ 100mA, 1A
Collector Cutoff Current: 100 nA
DC Current Gain (hFE): 300 @ 500mA, 5V
Maximum Power Dissipation: 500 mW
Transition Frequency: 150 MHz
Operating Temperature Range: -55°C to 150°C
Package: SOT-23-3 (TO-236-3, SC-59)
Mounting Type: Surface Mount
Product Status: Active
Compliance: ROHS3, REACH Unaffected

All substitute parts listed maintain these electrical and mechanical specifications, ensuring functional equivalence and direct replacement capability in existing circuit designs.

Parameter Comparison

Parameter	FMMT491AQTC	FMMT491AQTA	FMMT491ATA	FMMT491ATC
Manufacturer	Diodes Incorporated	Diodes Incorporated	Diodes Incorporated	Diodes Incorporated
Transistor Type	NPN	NPN	NPN	NPN
Current - Collector (Ic) Max	1 A	1 A	1 A	1 A
Voltage - Collector Emitter Breakdown (Max)	40 V	40 V	40 V	40 V
Vce Saturation (Max) @ Ib, Ic	500mV @ 100mA, 1A	500mV @ 100mA, 1A	500mV @ 100mA, 1A	500mV @ 100mA, 1A
Current - Collector Cutoff (Max)	100 nA	100 nA	100 nA	100 nA
DC Current Gain (hFE) Min @ Ic, Vce	300 @ 500mA, 5V	300 @ 500mA, 5V	300 @ 500mA, 5V	300 @ 500mA, 5V
Power - Max	500 mW	500 mW	500 mW	500 mW
Frequency - Transition	150 MHz	150 MHz	150 MHz	150 MHz
Operating Temperature Range	-55°C to 150°C	-55°C to 150°C	-55°C to 150°C	-55°C to 150°C
Package / Case	SOT-23-3	SOT-23-3	SOT-23-3	SOT-23-3
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Product Status	Active	Active	Active	Active
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
REACH Status	REACH Unaffected	REACH Unaffected	REACH Unaffected	REACH Unaffected

Engineering Selection Recommendations

All substitute parts listed—FMMT491AQTA, FMMT491ATA, and FMMT491ATC—are active production devices from Diodes Incorporated with identical electrical specifications and mechanical packaging to the FMMT491AQTC. Each part maintains AEC-Q101 automotive qualification status and ROHS3 compliance, ensuring regulatory and quality standards are preserved across substitution.

Selection between these parts is based on availability and supply chain requirements rather than electrical performance differences. The FMMT491ATA variant maintains the highest inventory level at 129,316 pieces, followed by FMMT491ATC at 11,097 pieces and FMMT491AQTA at 4,153 pieces. The original FMMT491AQTC maintains 760 pieces in stock.

All parts are suitable for direct replacement in automotive and industrial applications requiring NPN transistor functionality within the specified electrical and thermal operating ranges.

Frequently Asked Questions (FAQ)

Q: Can FMMT491AQTA, FMMT491ATA, and FMMT491ATC be used interchangeably with FMMT491AQTC?

A: Yes. All four parts share identical electrical parameters, including collector current rating (1 A), breakdown voltage (40 V), saturation voltage (500mV), current gain (300 @ 500mA, 5V), power dissipation (500 mW), and transition frequency (150 MHz). All are packaged in SOT-23-3 and operate across -55°C to 150°C. Direct substitution is valid without circuit modification.

Q: Are there differences in automotive qualification between these parts?

A: No. All substitute parts maintain AEC-Q101 qualification and automotive grade designation. Regulatory compliance and quality standards are equivalent across all listed variants.

Q: What is the significance of the part number suffix differences (AQTC, AQTA, ATA, ATC)?

A: The suffix designations reflect packaging and tape configuration variants within the FMMT491 product family. All variants maintain identical electrical specifications and SOT-23-3 physical packaging. Suffix differences do not affect electrical performance or substitution compatibility.

Q: Are moisture sensitivity levels identical across all variants?

A: FMMT491AQTA, FMMT491ATA, and FMMT491ATC are specified with MSL 1 (Unlimited). FMMT491AQTC does not list an MSL specification in the provided data. This does not affect substitution compatibility for standard handling and storage conditions.

Q: Can these parts be used in non-automotive applications?

A: Yes. While qualified for automotive use, these NPN transistors are suitable for general-purpose switching and amplification applications across industrial, consumer, and commercial markets within the specified electrical and thermal parameters.

Q: What is the recommended selection criterion when all parts are available?

A: Selection should be based on supply chain availability and lead time requirements. All parts are electrically and mechanically equivalent. FMMT491ATA offers the highest inventory availability, while FMMT491AQTC, FMMT491AQTA, and FMMT491ATC provide alternative sourcing options.

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