FMMT458TC Equivalent & Substitute Parts

Part Overview

The FMMT458TC is an NPN bipolar junction transistor manufactured by Diodes Incorporated, designed for surface mount applications in the SOT-23-3 package. This device operates at 400 V collector-emitter breakdown voltage with a maximum collector current of 225 mA and 500 mW power dissipation. The FMMT458TC is classified as obsolete product status. Identifying equivalent and substitute parts is necessary to maintain design continuity, ensure supply chain availability, and support ongoing production requirements for applications utilizing this transistor specification.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	400	V
Current - Collector (Ic) (Max)	225	mA
Power - Max	500	mW
Frequency - Transition	50	MHz
Vce Saturation (Max) @ Ib, Ic	500mV @ 6mA, 50mA	—
DC Current Gain (hFE) (Min) @ Ic, Vce	100 @ 50mA, 10V	—
Operating Temperature Range	-55 to 150	°C
Package / Case	SOT-23-3	—
Mounting Type	Surface Mount	—

Substitute Part Grouping Explanation

Substitute parts for the FMMT458TC are categorized based on electrical parameter compatibility and physical package equivalence. The primary substitution criteria are:

Parametric Equivalents (Direct Substitutes): Parts that maintain identical electrical specifications across all critical parameters including collector-emitter breakdown voltage (400 V), maximum collector current (225 mA), power dissipation (500 mW), transition frequency (50 MHz), saturation voltage characteristics, and DC current gain. These parts differ only in product status (active versus obsolete) or packaging format (tape & reel versus cut tape).

Manufacturer Recommended Alternatives: Parts that share the same SOT-23-3 package and surface mount technology but operate within different voltage and current ratings. These alternatives are suitable for applications where the design specifications permit operation at reduced voltage or current levels compared to the original FMMT458TC.

The following parameters determine substitution eligibility:

Transistor type (NPN)
Package type (SOT-23-3 / TO-236-3)
Mounting technology (Surface Mount)
Operating temperature range (-55°C to 150°C)
RoHS3 compliance and MSL rating

Parameter Comparison

Part Number	Manufacturer	Product Status	Vce Breakdown (V)	Ic Max (mA)	Power Max (mW)	Frequency (MHz)	hFE Min @ Ic, Vce	Package	Packaging Format
FMMT458TC	Diodes Incorporated	Obsolete	400	225	500	50	100 @ 50mA, 10V	SOT-23-3	Bulk
FMMT458QTA	Diodes Incorporated	Active	400	225	500	50	100 @ 50mA, 10V	SOT-23-3	Tape & Reel
FMMT458TA	Diodes Incorporated	Active	400	225	500	50	100 @ 50mA, 10V	SOT-23-3	Cut Tape & Digi-Reel
MMBT2484LT1G	onsemi	Active	60	100	225	—	250 @ 1mA, 5V	SOT-23-3	Cut Tape & Digi-Reel
MMBT2484LT3G	onsemi	Active	60	100	225	—	250 @ 1mA, 5V	SOT-23-3	Tape & Reel
MMBT6429LT1G	onsemi	Active	45	200	225	700	500 @ 100µA, 5V	SOT-23-3	Tape & Reel
PBHV8115T,215	NXP Semiconductors	Active	150	1000	300	30	50 @ 500mA, 10V	SOT-23-3	Bulk
PMBTA44,215	Nexperia USA Inc.	Active	400	300	250	20	50 @ 10mA, 10V	SOT-23-3	Tape & Reel

Engineering Selection Recommendations

Direct Replacement (Parametric Equivalents):

FMMT458QTA and FMMT458TA are direct parametric equivalents to the FMMT458TC. Both parts are manufactured by Diodes Incorporated with active product status, ensuring long-term availability and supply chain stability. These parts maintain identical electrical specifications and are suitable for one-to-one replacement in existing designs. The primary distinction between these equivalents is packaging format: FMMT458QTA is supplied in tape & reel format, while FMMT458TA is available in cut tape and Digi-Reel format. Selection between these options depends on production volume and assembly line requirements.

Alternative Substitutes (Reduced Specifications):

MMBT2484LT1G and MMBT2484LT3G (onsemi) are manufacturer-recommended alternatives for applications where collector-emitter voltage requirements do not exceed 60 V and collector current does not exceed 100 mA. These parts operate at reduced power dissipation (225 mW) and are available from an active manufacturer with established supply channels.

MMBT6429LT1G (onsemi) operates at 45 V collector-emitter breakdown with 200 mA maximum collector current. This part features significantly higher transition frequency (700 MHz) compared to the FMMT458TC (50 MHz), making it suitable for higher-frequency applications within its voltage and current constraints.

PBHV8115T,215 (NXP Semiconductors) operates at 150 V collector-emitter breakdown with 1 A maximum collector current. This part is suitable for applications requiring higher current handling at reduced voltage levels.

PMBTA44,215 (Nexperia USA Inc.) maintains the 400 V collector-emitter breakdown voltage specification of the FMMT458TC but with increased maximum collector current (300 mA) and reduced power dissipation (250 mW). This part is suitable for designs requiring higher current capacity at the same voltage rating.

All substitute parts maintain SOT-23-3 package compatibility, surface mount technology, RoHS3 compliance, and MSL rating of 1 (unlimited moisture sensitivity level).

Frequently Asked Questions (FAQ)

Q: Can FMMT458QTA or FMMT458TA be used as direct replacements for FMMT458TC?

A: Yes. FMMT458QTA and FMMT458TA are parametric equivalents with identical electrical specifications. The only differences are product status (active versus obsolete) and packaging format. Both parts are suitable for direct substitution in existing designs without circuit modification.

Q: What is the difference between FMMT458QTA and FMMT458TA?

A: Both parts are electrically identical. FMMT458QTA is supplied in tape & reel packaging, while FMMT458TA is supplied in cut tape and Digi-Reel format. Selection depends on production volume and assembly equipment compatibility.

Q: Can MMBT2484LT1G or MMBT2484LT3G replace FMMT458TC in all applications?

A: No. These onsemi parts operate at maximum 60 V collector-emitter breakdown voltage and 100 mA collector current, compared to the FMMT458TC specifications of 400 V and 225 mA. These alternatives are suitable only for applications where the design specifications permit operation within these reduced voltage and current limits.

Q: What are the key differences between MMBT6429LT1G and FMMT458TC?

A: MMBT6429LT1G operates at 45 V collector-emitter breakdown (versus 400 V), 200 mA maximum collector current (versus 225 mA), and features 700 MHz transition frequency (versus 50 MHz). This part is suitable for high-frequency applications operating at lower voltage levels.

Q: Is PMBTA44,215 a suitable substitute for FMMT458TC?

A: PMBTA44,215 maintains the 400 V collector-emitter breakdown voltage but operates at reduced transition frequency (20 MHz versus 50 MHz) and reduced power dissipation (250 mW versus 500 mW). This part is suitable for applications where the reduced frequency and power specifications are acceptable.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. All substitute parts listed maintain RoHS3 compliance and MSL rating of 1 (unlimited moisture sensitivity level), consistent with the FMMT458TC specifications.

Q: Can substitute parts with different voltage ratings be used interchangeably?

A: No. Substitute parts must be selected based on the specific voltage and current requirements of the application circuit. Parts with lower voltage ratings (such as MMBT2484 at 60 V or MMBT6429 at 45 V) cannot be used in circuits designed for 400 V operation.

Q: What packaging formats are available for equivalent parts?

A: FMMT458QTA is available in tape & reel format. FMMT458TA is available in cut tape and Digi-Reel format. Selection depends on production volume, assembly line equipment, and inventory management requirements.

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