FMMTA42TC Equivalent & Substitute Parts

Part Overview

The FMMTA42TC is an NPN bipolar junction transistor manufactured by Diodes Incorporated, designed for surface mount applications in the SOT-23-3 package. This device is rated for 300 V collector-emitter breakdown voltage with a maximum collector current of 200 mA and 330 mW power dissipation. The FMMTA42TC is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and production continuity. Active alternatives with identical or enhanced electrical characteristics are available from multiple manufacturers.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	300	V
Current - Collector (Ic) (Max)	200	mA
Power - Max	330	mW
Frequency - Transition	50	MHz
DC Current Gain (hFE) (Min) @ Ic, Vce	40 @ 30mA, 10V	—
Vce Saturation (Max) @ Ib, Ic	500mV @ 2mA, 20mA	—
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 FMMTA42TC is determined by the following critical electrical and mechanical parameters:

Primary Substitution Criteria:

Transistor Type: NPN
Voltage - Collector Emitter Breakdown (Max): 300 V minimum
Current - Collector (Ic) (Max): 200 mA minimum
Package / Case: SOT-23-3 (TO-236-3, SC-59) or compatible surface mount package
Operating Temperature Range: -55°C to 150°C minimum
DC Current Gain (hFE) (Min): 40 @ 30mA, 10V minimum
Vce Saturation (Max): 500mV @ 2mA, 20mA maximum

Substitute Categories:

Category 1: Direct Electrical Equivalents (SOT-23-3 Package) Parts meeting all primary criteria with identical or superior electrical performance in the same SOT-23-3 package. These include FMMTA42TA, MMBTA42,215, MMBTA42-TP, MMBTA42LT1G, and MMBTA42LT3G.

Category 2: Enhanced Current Rating (SOT-23-3 Package) Parts with 500 mA collector current rating (exceeding the 200 mA requirement) while maintaining 300 V breakdown voltage and SOT-23-3 packaging. These include MMBTA42-7-F and MMBTA42LT1G/LT3G variants.

Category 3: Reduced Package Size (SOT-323) The MMSTA42-7-F provides equivalent electrical performance in the smaller SOT-323 package, suitable for space-constrained applications.

Category 4: Lower Voltage Applications Parts with reduced voltage ratings (45 V or 60 V) are listed for reference but are not direct substitutes for 300 V applications. These include MMBT2484LT1G, MMBT2484LT3G, and MMBT6429LT1G.

Parameter Comparison

Part Number	Manufacturer	Status	Ic (Max) mA	Vce(br) V	Power mW	Package	hFE (Min)	Vce Sat mV
FMMTA42TC	Diodes Inc.	Obsolete	200	300	330	SOT-23-3	40	500
FMMTA42TA	Diodes Inc.	Active	200	300	330	SOT-23-3	40	500
MMBTA42-7-F	Diodes Inc.	Active	500	300	300	SOT-23-3	40	500
MMSTA42-7-F	Diodes Inc.	Active	200	300	200	SOT-323	40	500
MMBT2484LT1G	onsemi	Active	100	60	225	SOT-23-3	250	350
MMBT2484LT3G	onsemi	Active	100	60	225	SOT-23-3	250	350
MMBT6429LT1G	onsemi	Active	200	45	225	SOT-23-3	500	600
MMBTA42,215	Nexperia USA Inc.	Active	100	300	250	SOT-23-3	40	500
MMBTA42-TP	Micro Commercial Co	Active	500	300	225	SOT-23-3	40	500
MMBTA42LT1G	onsemi	Active	500	300	225	SOT-23-3	40	500
MMBTA42LT3G	onsemi	Active	500	300	225	SOT-23-3	40	500

Engineering Selection Recommendations

Recommended Primary Substitutes for Direct Replacement:

The FMMTA42TA (Diodes Incorporated, Active status) is the direct equivalent to the obsolete FMMTA42TC. Both parts share identical electrical specifications and packaging. The FMMTA42TA is available in higher inventory quantities and maintains active product status, making it the preferred choice for immediate replacement.

Recommended Substitutes for Enhanced Performance:

The MMBTA42LT1G and MMBTA42LT3G (onsemi, Active status) provide superior current handling capability at 500 mA while maintaining the 300 V breakdown voltage specification. These parts are suitable for applications requiring higher collector current margins. Both variants are ROHS3 compliant with MSL 1 rating.

The MMBTA42-7-F (Diodes Incorporated, Active status) offers equivalent enhanced current rating with 500 mA capability and maintains full electrical compatibility with the original specification.

Recommended Substitute for Space-Constrained Applications:

The MMSTA42-7-F (Diodes Incorporated, Active status) provides identical electrical performance in the smaller SOT-323 package. This option is suitable for designs where PCB real estate is limited, provided the smaller package footprint is compatible with assembly equipment and design layout.

Substitutes Not Recommended for 300 V Applications:

The MMBT2484LT1G, MMBT2484LT3G, and MMBT6429LT1G are not suitable direct replacements due to reduced voltage ratings (60 V and 45 V respectively). These parts are listed for reference only and should not be used in circuits requiring 300 V breakdown voltage capability.

All recommended substitutes maintain ROHS3 compliance, MSL 1 rating, and operating temperature range of -55°C to 150°C, ensuring compatibility with existing design requirements and regulatory standards.

Frequently Asked Questions (FAQ)

Q: Can the FMMTA42TA be used as a direct replacement for the FMMTA42TC?

A: Yes. The FMMTA42TA is electrically and mechanically identical to the FMMTA42TC. Both parts feature 300 V breakdown voltage, 200 mA maximum collector current, SOT-23-3 packaging, and identical DC current gain specifications. The FMMTA42TA is currently in active production status with higher inventory availability.

Q: What is the difference between MMBTA42LT1G and MMBTA42LT3G?

A: Both parts are manufactured by onsemi and share identical electrical specifications: 500 mA collector current, 300 V breakdown voltage, and SOT-23-3 packaging. The designation difference reflects packaging variants (Cut Tape vs. Tape & Reel). Electrical performance is equivalent; selection depends on procurement and assembly requirements.

Q: Can I use MMBTA42-7-F in place of FMMTA42TC?

A: Yes, with design consideration. The MMBTA42-7-F maintains the 300 V breakdown voltage and SOT-23-3 package compatibility. However, it provides 500 mA maximum collector current compared to the original 200 mA specification. This enhanced current rating does not create incompatibility; the part operates within the original circuit's current requirements while providing additional margin.

Q: Why are MMBT2484LT1G and MMBT6429LT1G listed if they cannot replace FMMTA42TC?

A: These parts are included for reference and historical context. They share the same SOT-23-3 package and NPN transistor type but feature reduced voltage ratings (60 V and 45 V respectively). They are not suitable for 300 V applications and should not be selected as substitutes for the FMMTA42TC.

Q: Is the MMSTA42-7-F a suitable substitute if my PCB layout permits the SOT-323 package?

A: Yes. The MMSTA42-7-F provides identical electrical performance to the FMMTA42TC: 300 V breakdown voltage, 200 mA collector current, 40 minimum hFE, and 500 mV saturation voltage. The SOT-323 package is physically smaller than SOT-23-3, making it suitable for space-constrained designs. Verify that your assembly equipment and PCB layout support SOT-323 footprints before selection.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All substitute parts listed in this reference maintain ROHS3 compliance and MSL 1 (Unlimited) moisture sensitivity rating, ensuring compatibility with current manufacturing standards and environmental regulations.

Q: What is the primary reason to select MMBTA42-TP over other 500 mA alternatives?

A: The MMBTA42-TP is manufactured by Micro Commercial Co and provides 500 mA collector current with 300 V breakdown voltage in SOT-23-3 packaging. Selection depends on supplier availability, lead time, and procurement agreements. Electrically, it is equivalent to MMBTA42LT1G and MMBTA42-7-F.

Q: Can I mix different substitute part numbers in the same production run?

A: All recommended substitutes share identical electrical specifications and package compatibility. However, mixing part numbers from different manufacturers in the same production run may introduce traceability and quality documentation complexity. Standardize on a single part number per design revision when possible.

Q: What should I verify before finalizing a substitute part selection?

A: Confirm the following: (1) Collector current requirement does not exceed the substitute part's maximum rating; (2) Collector-emitter breakdown voltage meets or exceeds 300 V; (3) Package footprint (SOT-23-3 or SOT-323) is compatible with PCB layout and assembly equipment; (4) Operating temperature range includes your application's requirements; (5) Supplier inventory and lead time meet production schedules; (6) ROHS and REACH compliance status matches your regulatory requirements.

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