FMMT618TC Equivalent & Substitute Parts

Part Overview

The FMMT618TC is a Surface Mount NPN Bipolar Junction Transistor manufactured by Diodes Incorporated, rated for 20V collector-emitter breakdown voltage and 2.5A maximum collector current. This device is packaged in SOT-23-3 (TO-236-3) configuration and is currently classified as Obsolete. Due to its obsolete status, equivalent substitute parts from active product lines are necessary for new designs and ongoing production requirements. The FMMT618TC operates across a temperature range of -55°C to 150°C with a maximum power dissipation of 625 mW and transition frequency of 140 MHz.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	20	V
Current - Collector (Ic) (Max)	2.5	A
Power - Max	625	mW
Frequency - Transition	140	MHz
Vce Saturation (Max) @ Ib, Ic	200mV @ 50mA, 2.5A	—
DC Current Gain (hFE) (Min) @ Ic, Vce	200 @ 2A, 2V	—
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 FMMT618TC is determined by strict equivalence across the following critical parameters:

Primary Equivalence Criteria:

Transistor Type: NPN
Package / Case: SOT-23-3 (TO-236-3, SC-59)
Mounting Type: Surface Mount
Voltage - Collector Emitter Breakdown (Max): ≥ 20V
Current - Collector (Ic) (Max): ≥ 2.5A
Operating Temperature Range: -55°C to 150°C minimum
RoHS Status: ROHS3 Compliant

Secondary Compatibility Parameters:

Power - Max: ≥ 625 mW
Frequency - Transition: ≥ 140 MHz
DC Current Gain (hFE): ≥ 200 @ specified conditions
Vce Saturation: ≤ 200 mV @ rated conditions

Substitute parts are grouped into two categories:

Category 1 - Direct Parametric Equivalents: Parts meeting or exceeding all primary and secondary criteria with identical or superior electrical performance.

Category 2 - Functional Alternatives: Parts meeting primary equivalence criteria but with trade-offs in secondary parameters, suitable for applications with relaxed performance requirements.

Parameter Comparison

Parameter	FMMT618TC	FMMT618TA	NSS20201LT1G	NSV20201LT1G	MMBT6429LT1G	MMBT2484LT1G	MMBT2484LT3G	BFS19,215	PBSS4120T,215
Manufacturer	Diodes Inc.	Diodes Inc.	onsemi	onsemi	onsemi	onsemi	onsemi	Nexperia	Nexperia
Product Status	Obsolete	Active	Active	Active	Active	Active	Active	Active	Active
Transistor Type	NPN	NPN	NPN	NPN	NPN	NPN	NPN	NPN	NPN
Voltage - Collector Emitter Breakdown (Max)	20V	20V	20V	20V	45V	60V	60V	20V	20V
Current - Collector (Ic) (Max)	2.5A	2.5A	2A	2A	200mA	100mA	100mA	30mA	1A
Power - Max	625mW	625mW	460mW	460mW	225mW	225mW	225mW	250mW	480mW
Frequency - Transition	140MHz	140MHz	150MHz	150MHz	700MHz	—	—	260MHz	100MHz
Vce Saturation (Max) @ Ib, Ic	200mV @ 50mA, 2.5A	200mV @ 50mA, 2.5A	100mV @ 200mA, 2A	100mV @ 200mA, 2A	600mV @ 5mA, 100mA	350mV @ 100µA, 1mA	350mV @ 100µA, 1mA	—	250mV @ 50mA, 1A
DC Current Gain (hFE) (Min) @ Ic, Vce	200 @ 2A, 2V	200 @ 2A, 2V	200 @ 500mA, 2V	200 @ 500mA, 2V	500 @ 100µA, 5V	250 @ 1mA, 5V	250 @ 1mA, 5V	65 @ 1mA, 10V	300 @ 500mA, 2V
Operating Temperature Range	-55 to 150°C	-55 to 150°C	-55 to 150°C	-55 to 150°C	-55 to 150°C	-55 to 150°C	-55 to 150°C	150°C (Max)	150°C (Max)
Package / Case	SOT-23-3	SOT-23-3	SOT-23-3	SOT-23-3	SOT-23-3	SOT-23-3	SOT-23-3	TO-236AB	TO-236AB
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)
Automotive Grade	—	—	—	—	—	—	—	Yes (AEC-Q101)	Yes (AEC-Q100)

Engineering Selection Recommendations

Direct Replacement (Category 1):

The FMMT618TA from Diodes Incorporated is the primary direct replacement for the obsolete FMMT618TC. This part is electrically identical across all critical parameters: 20V breakdown voltage, 2.5A maximum collector current, 625 mW power dissipation, and 140 MHz transition frequency. The FMMT618TA maintains the same DC current gain specification (200 @ 2A, 2V) and saturation voltage (200 mV @ 50mA, 2.5A). The part is currently in Active product status with substantial inventory availability (54,762 pieces). Packaging is identical (SOT-23-3), and compliance certifications match (ROHS3, MSL 1). This substitution requires no circuit modifications.

High-Current Alternatives (Category 1):

The NSS20201LT1G and NSV20201LT1G from onsemi provide functional equivalence with slightly reduced maximum collector current (2A versus 2.5A) and power dissipation (460 mW versus 625 mW). Both parts maintain the 20V breakdown voltage rating and -55°C to 150°C operating range. These devices feature improved saturation voltage performance (100 mV @ 200mA, 2A) compared to the FMMT618TC. Both parts are in Active status with good inventory levels. Selection of these alternatives is appropriate for applications where the 2A current rating is sufficient.

Reduced-Current Alternatives (Category 2):

The MMBT6429LT1G from onsemi offers a 45V breakdown voltage with 200 mA maximum collector current. This part is suitable for applications requiring higher voltage capability but lower current handling. The PBSS4120T,215 from Nexperia provides 1A maximum collector current at 20V breakdown voltage with automotive-grade qualification (AEC-Q100). This part is appropriate for automotive applications where the 1A current rating is acceptable.

Not Recommended for Direct Substitution:

The MMBT2484LT1G and MMBT2484LT3G devices feature 60V breakdown voltage but only 100 mA maximum collector current, representing a significant reduction in current-handling capability. The BFS19,215 from Nexperia is limited to 30 mA maximum collector current and is unsuitable for applications requiring the 2.5A capability of the FMMT618TC.

Compliance and Certification:

All substitute parts maintain ROHS3 compliance and MSL 1 (Unlimited) moisture sensitivity rating. The Nexperia devices (BFS19,215 and PBSS4120T,215) carry automotive-grade qualifications (AEC-Q101 and AEC-Q100 respectively), making them suitable for automotive applications where such certification is required.

Frequently Asked Questions (FAQ)

Q: Can the FMMT618TA be used as a direct replacement for the FMMT618TC?

A: Yes. The FMMT618TA is electrically and mechanically identical to the FMMT618TC across all specified parameters. The primary difference is product status: FMMT618TA is Active while FMMT618TC is Obsolete. No circuit modifications are required.

Q: What is the difference between FMMT618TA and NSS20201LT1G?

A: Both parts operate at 20V breakdown voltage and share the same SOT-23-3 package. The key difference is maximum collector current: FMMT618TA supports 2.5A while NSS20201LT1G supports 2A. NSS20201LT1G offers superior saturation voltage performance (100 mV versus 200 mV at rated conditions). Selection depends on whether the application requires the full 2.5A capability.

Q: Are the Nexperia parts (BFS19,215 and PBSS4120T,215) suitable replacements?

A: These parts are suitable only for applications with reduced current requirements. BFS19,215 is limited to 30 mA and PBSS4120T,215 to 1A, both significantly below the 2.5A rating of the FMMT618TC. However, both Nexperia devices carry automotive-grade qualifications if such certification is required.

Q: What does "Obsolete" product status mean for the FMMT618TC?

A: Obsolete status indicates the manufacturer has discontinued production and support for this part. Existing inventory may be available from distributors, but long-term supply cannot be guaranteed. Migration to an Active substitute part is necessary for new designs and ongoing production.

Q: Are all substitute parts available in the same SOT-23-3 package?

A: All listed substitute parts are available in SOT-23-3 or equivalent TO-236-3 packaging. The Nexperia devices (BFS19,215 and PBSS4120T,215) are designated as TO-236AB, which is mechanically and electrically compatible with SOT-23-3. No PCB layout modifications are required.

Q: What is the significance of the DC Current Gain (hFE) specification?

A: DC Current Gain indicates the amplification factor of the transistor. The FMMT618TC specifies a minimum hFE of 200 @ 2A, 2V. Most substitute parts meet or exceed this specification at their rated conditions. Higher hFE values (such as 500 in MMBT6429LT1G) indicate greater amplification capability but do not affect basic substitutability if the application does not depend on specific gain characteristics.

Q: Can MMBT2484LT1G or MMBT2484LT3G be used as substitutes?

A: These parts are not recommended as direct substitutes due to significantly reduced maximum collector current (100 mA versus 2.5A) and lower power dissipation (225 mW versus 625 mW). They are suitable only for applications with substantially lower current requirements. The higher 60V breakdown voltage provides no benefit if the circuit operates at 20V or below.

Q: What is the difference between Cut Tape (CT) and Tape & Reel (TR) packaging?

A: Both are surface mount delivery formats. Cut Tape (CT) provides individual components or small quantities on tape. Tape & Reel (TR) provides components on continuous reel for automated assembly. Electrical and mechanical specifications are identical; the difference is in quantity and handling for production environments.

Q: Are RoHS and REACH compliance requirements met by all substitutes?

A: Yes. All listed substitute parts are ROHS3 Compliant and REACH Unaffected, matching the compliance status of the FMMT618TC. This ensures compatibility with environmental and regulatory requirements across all regions.

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