FMMT491TC Equivalent & Substitute Parts

Part Overview

The FMMT491TC is an NPN bipolar junction transistor manufactured by Diodes Incorporated, designed for general-purpose switching and amplification applications. This surface mount device operates at 60 V collector-emitter breakdown voltage with a maximum collector current of 1 A and 500 mW power dissipation. The part is classified as Active product status with full RoHS3 compliance and unlimited moisture sensitivity rating. Equivalent and substitute parts are identified to provide design flexibility, accommodate supply chain variations, and support alternative packaging or performance requirements while maintaining functional compatibility within specified electrical parameters.

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
DC Current Gain (hFE) (Min) @ Ic, Vce	100 @ 500mA, 5V	—
Vce Saturation (Max) @ Ib, Ic	250mV @ 100mA, 1A	—
Current - Collector Cutoff (Max)	100	nA
Operating Temperature Range	-55 to 150	°C
Package / Case	SOT-23-3	—
Mounting Type	Surface Mount	—
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitute parts for the FMMT491TC are classified into three categories based on electrical and mechanical compatibility:

Direct Manufacturer Substitutes maintain identical or superior electrical specifications across all critical parameters: 60 V collector-emitter breakdown voltage, 1 A maximum collector current, 150 MHz transition frequency, NPN configuration, and SOT-23-3 package. These parts differ only in packaging format (Tape & Reel versus Cut Tape) or minor variations in power dissipation and saturation voltage that do not affect functional operation within the specified design envelope.

Parametric Equivalents share the same base product number (FMMT491) but differ in packaging designation or tape format. These parts are electrically identical to the main part and represent alternative sourcing options from the same manufacturer with identical electrical performance.

Manufacturer-Recommended Alternatives are parts from different manufacturers that operate within the same voltage and current specifications but may have different package styles, transition frequencies, or current ratings. These parts are suitable for applications where the primary design constraints are voltage and current handling capability rather than specific frequency response or package format.

The following key parameters determine substitution eligibility:

Voltage - Collector Emitter Breakdown (Max): 60 V minimum
Current - Collector (Ic) (Max): 1 A minimum
Transistor Type: NPN
Package / Case: SOT-23-3 or compatible surface mount package
Operating Temperature Range: -55°C to 150°C minimum
RoHS3 Compliance: Required

Parameter Comparison

Part Number	Manufacturer	Ic (Max)	Vce Breakdown (Max)	Power (Max)	fT (MHz)	hFE (Min)	Vce Sat (Max)	Package	Packaging Format
FMMT491TC	Diodes Incorporated	1 A	60 V	500 mW	150	100	250mV	SOT-23-3	Tape & Reel
DNBT8105-7	Diodes Incorporated	1 A	60 V	600 mW	150	100	500mV	SOT-23-3	Cut Tape & Digi-Reel
ZXTN2038FTA	Diodes Incorporated	1 A	60 V	350 mW	150	100	500mV	SOT-23-3	Tape & Reel
FMMT491QTA	Diodes Incorporated	1 A	60 V	500 mW	150	100	250mV	SOT-23-3	Tape & Reel
FMMT491TA	Diodes Incorporated	1 A	60 V	500 mW	150	100	250mV	SOT-23-3	Cut Tape & Digi-Reel
FMMT491-TP	Micro Commercial Co	1 A	60 V	500 mW	150	100	500mV	SOT-23-3	Tape & Reel
2SC5866TLQ	Rohm Semiconductor	2 A	60 V	500 mW	200	120	500mV	TSMT3	Cut Tape & Digi-Reel
BC846,215	NXP USA Inc.	100 mA	65 V	250 mW	100	110	400mV	SOT-23-3	—
BC846A,215	Nexperia USA Inc.	100 mA	65 V	250 mW	100	110	400mV	SOT-23-3	Tape & Reel
BC846ALT1G	onsemi	100 mA	65 V	300 mW	100	110	600mV	SOT-23-3	Cut Tape & Digi-Reel
BC846B,215	Nexperia USA Inc.	100 mA	65 V	250 mW	100	200	400mV	SOT-23-3	Cut Tape & Digi-Reel

Engineering Selection Recommendations

Direct Substitutes (Recommended for Drop-In Replacement)

FMMT491QTA and FMMT491TA are parametric equivalents manufactured by Diodes Incorporated with identical electrical specifications to the FMMT491TC. Both parts maintain 1 A collector current, 60 V breakdown voltage, 500 mW power dissipation, and 150 MHz transition frequency. FMMT491QTA is supplied in Tape & Reel format, while FMMT491TA is supplied in Cut Tape & Digi-Reel format. Both are Active product status with ROHS3 compliance and unlimited moisture sensitivity rating. These parts are suitable for direct substitution without circuit modification.

DNBT8105-7 from Diodes Incorporated provides superior power dissipation (600 mW) and is available in Cut Tape & Digi-Reel packaging. This part maintains all critical electrical parameters and is suitable for applications requiring higher thermal margin. The increased saturation voltage (500mV versus 250mV) is within acceptable limits for most switching applications.

ZXTN2038FTA from Diodes Incorporated is suitable for applications with lower power requirements, offering 350 mW dissipation while maintaining full 1 A collector current and 60 V breakdown voltage. This part is available in Tape & Reel format and is appropriate for space-constrained or thermally sensitive designs.

FMMT491-TP from Micro Commercial Co maintains identical electrical specifications and is available in Tape & Reel packaging. This part is suitable for applications where multi-source qualification is required.

Alternative Substitutes (Application-Dependent)

2SC5866TLQ from Rohm Semiconductor is suitable for applications requiring higher collector current (2 A) or improved transition frequency (200 MHz). This part operates at 60 V breakdown voltage and 500 mW power dissipation. The TSMT3 package differs from SOT-23-3 and requires PCB layout modification. This part is recommended only when higher current capability is required.

BC846 series transistors from NXP/Nexperia and onsemi are small-signal devices with maximum collector current of 100 mA. These parts are not suitable for applications requiring 1 A collector current. The BC846 series is appropriate only for low-current signal amplification or switching applications where the FMMT491TC is over-specified.

All substitute parts listed maintain Active product status and ROHS3 compliance. Selection should be based on packaging format availability, supply chain requirements, and specific application current and power dissipation needs.

Frequently Asked Questions (FAQ)

Q: Can DNBT8105-7 be used as a direct replacement for FMMT491TC?

A: Yes. DNBT8105-7 maintains identical voltage (60 V), current (1 A), and frequency (150 MHz) specifications. The primary differences are packaging format (Cut Tape & Digi-Reel versus Tape & Reel) and increased power dissipation (600 mW versus 500 mW). The higher saturation voltage (500mV versus 250mV) is acceptable for most switching applications. Verify packaging compatibility with your assembly equipment before implementation.

Q: Are BC846 series transistors suitable replacements for FMMT491TC?

A: No. BC846 series transistors are rated for maximum 100 mA collector current, while FMMT491TC is rated for 1 A. BC846 devices are small-signal transistors suitable only for low-current applications. Using BC846 in a circuit designed for 1 A operation will result in device failure or inadequate performance.

Q: What is the difference between FMMT491TC, FMMT491QTA, and FMMT491TA?

A: All three parts are manufactured by Diodes Incorporated with identical electrical specifications. The differences are in packaging format: FMMT491TC and FMMT491QTA are supplied in Tape & Reel format, while FMMT491TA is supplied in Cut Tape & Digi-Reel format. Selection depends on your assembly process requirements and equipment compatibility.

Q: Can ZXTN2038FTA be used in high-power applications?

A: ZXTN2038FTA is rated for 350 mW maximum power dissipation, compared to 500 mW for FMMT491TC. This part is suitable for applications where power dissipation is below 350 mW. For applications requiring sustained operation near 500 mW, use FMMT491TC, FMMT491QTA, FMMT491TA, or DNBT8105-7.

Q: Is the SOT-23-3 package compatible across all listed substitutes?

A: Most substitutes use SOT-23-3 packaging. The exception is 2SC5866TLQ, which uses TSMT3 package. Verify package compatibility with your PCB design and assembly equipment. SOT-23-3 and TO-236-3 designations refer to the same physical package.

Q: What are the compliance and certification requirements for these parts?

A: All listed substitute parts maintain ROHS3 compliance and are classified as Active product status. Moisture sensitivity level is 1 (Unlimited) for all parts except where not specified. REACH status is Unaffected for all parts. ECCN classification is EAR99 for all parts. Verify specific compliance requirements for your application and region.

Q: Can FMMT491-TP from Micro Commercial Co be used interchangeably with FMMT491TC?

A: Yes. FMMT491-TP maintains identical electrical specifications (1 A, 60 V, 500 mW, 150 MHz) and SOT-23-3 packaging. The primary difference is manufacturer and packaging format (Tape & Reel). This part is suitable for applications requiring multi-source qualification or when Diodes Incorporated supply is unavailable.

Q: What is the significance of the saturation voltage difference between FMMT491TC (250mV) and DNBT8105-7 (500mV)?

A: Saturation voltage affects the voltage drop across the transistor when fully conducting. FMMT491TC has lower saturation voltage (250mV), resulting in lower power dissipation in saturated switching applications. DNBT8105-7 with 500mV saturation voltage will dissipate approximately twice the power in the same application. Select based on your circuit's power budget and thermal requirements.

Q: Are there any temperature range differences between substitutes?

A: FMMT491TC, DNBT8105-7, ZXTN2038FTA, FMMT491QTA, and FMMT491TA all operate from -55°C to 150°C. BC846ALT1G also operates across this full range. Other BC846 variants and 2SC5866TLQ specify only maximum temperature of 150°C without minimum specification. Verify temperature range requirements for your application before selection.

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