MMBTA42 Equivalent & Substitute Parts

Part Overview

The MMBTA42 is a surface-mount NPN bipolar junction transistor manufactured by STMicroelectronics in SOT-23 packaging. This device is rated for 300 V collector-emitter breakdown voltage with a maximum collector current of 100 mA and 350 mW power dissipation. The MMBTA42 operates across a temperature range of -65°C to 150°C and features a 50 MHz transition frequency.

The MMBTA42 is classified as obsolete. Equivalent and substitute parts are necessary to maintain design continuity, ensure supply chain availability, and support ongoing production requirements. Active alternatives with comparable 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)	100	mA
Power - Max	350	mW
Frequency - Transition	50	MHz
Operating Temperature Range	-65 to 150	°C
Package / Case	SOT-23-3 (TO-236)	—
Mounting Type	Surface Mount	—
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitute parts for the MMBTA42 are classified into two categories based on electrical parameter alignment:

Direct Substitutes maintain the same collector-emitter breakdown voltage (300 V) and transition frequency (50 MHz) as the original part. These parts are functionally interchangeable within the same circuit topology and design constraints.

Similar Substitutes share the same package format (SOT-23-3) and NPN transistor type but differ in one or more key electrical parameters. These parts are suitable for applications where the specific parameter deviation does not impact circuit performance.

The critical parameters determining substitution eligibility are:

Voltage - Collector Emitter Breakdown (Max): 300 V minimum for direct substitutes
Current - Collector (Ic) (Max): 100 mA minimum for direct substitutes
Frequency - Transition: 50 MHz minimum
Package / Case: SOT-23-3 (TO-236) surface mount
Operating Temperature Range: -55°C to 150°C minimum
RoHS3 Compliance and MSL Level 1 (Unlimited)

Parameter Comparison

Part Number	Manufacturer	Status	Vce Breakdown (V)	Ic Max (mA)	Power Max (mW)	Freq (MHz)	Temp Range (°C)	Package
MMBTA42	STMicroelectronics	Obsolete	300	100	350	50	-65 to 150	SOT-23-3
MMBTA42-7-F	Diodes Incorporated	Active	300	500	300	50	-55 to 150	SOT-23-3
MMBTA42LT1G	onsemi	Active	300	500	225	50	-55 to 150	SOT-23-3
SMMBTA42LT3G	onsemi	Active	300	500	225	50	-55 to 150	SOT-23-3
BSR19A,215	Nexperia USA Inc.	Active	160	300	250	300	-55 to 150	SOT-23-3
DN350T05-7	Diodes Incorporated	Active	350	500	300	50	-55 to 150	SOT-23-3
FMMT497TA	Diodes Incorporated	Active	300	500	500	75	-55 to 150	SOT-23-3
FMMT6517TA	Diodes Incorporated	Active	350	500	330	50	-55 to 150	SOT-23-3
FMMTA42TA	Diodes Incorporated	Active	300	200	330	50	-55 to 150	SOT-23-3
MMBT2484LT1G	onsemi	Active	60	100	225	—	-55 to 150	SOT-23-3
MMBT2484LT3G	onsemi	Active	60	100	225	—	-55 to 150	SOT-23-3

Engineering Selection Recommendations

Direct Substitutes (Recommended for Pin-Compatible Replacement)

The following parts are classified as direct substitutes and maintain electrical compatibility with the MMBTA42 design envelope:

MMBTA42LT1G (onsemi): Active status with 205,200 units in stock. Maintains 300 V breakdown voltage and 50 MHz transition frequency. Supports collector current up to 500 mA, exceeding original specification. ROHS3 compliant with MSL Level 1.
SMMBTA42LT3G (onsemi): Active status with 16,965 units in stock. Identical electrical specifications to MMBTA42LT1G. Supplied in Tape & Reel packaging. ROHS3 compliant with MSL Level 1.
MMBTA42-7-F (Diodes Incorporated): Active status with 17,100 units in stock. Maintains 300 V breakdown voltage and 50 MHz transition frequency. Supports collector current up to 500 mA. ROHS3 compliant with MSL Level 1.

Similar Substitutes (Application-Dependent Selection)

The following parts share the SOT-23-3 package and NPN configuration but exhibit parameter deviations requiring circuit evaluation:

FMMT497TA (Diodes Incorporated): 300 V breakdown voltage with enhanced 75 MHz transition frequency and 500 mW power rating. Suitable for applications requiring higher frequency performance. Active status with 50,100 units in stock.
DN350T05-7 (Diodes Incorporated): 350 V breakdown voltage with 500 mA collector current capability. Applicable to designs requiring higher voltage margin. Active status with 35,390 units in stock.
FMMT6517TA (Diodes Incorporated): 350 V breakdown voltage with 500 mA collector current and 330 mW power rating. Active status with 3,687 units in stock.
FMMTA42TA (Diodes Incorporated): 300 V breakdown voltage with 200 mA collector current and 330 mW power rating. Suitable for current-limited applications. Active status with 18,404 units in stock.

Not Recommended for Direct Substitution

BSR19A,215 (Nexperia USA Inc.): 160 V breakdown voltage falls below the 300 V specification of the original part. Suitable only for applications with reduced voltage requirements.
MMBT2484LT1G and MMBT2484LT3G (onsemi): 60 V breakdown voltage is insufficient for 300 V circuit operation. Not suitable for direct substitution.

All recommended substitutes maintain ROHS3 compliance, MSL Level 1 moisture sensitivity, and surface-mount SOT-23-3 packaging compatibility.

Frequently Asked Questions (FAQ)

Q: Can MMBTA42LT1G be used as a direct replacement for MMBTA42?

A: Yes. MMBTA42LT1G maintains the same 300 V collector-emitter breakdown voltage, 50 MHz transition frequency, and SOT-23-3 package format. The part supports higher collector current (500 mA vs. 100 mA), which does not create compatibility issues in circuits designed for the original 100 mA specification. Both parts are ROHS3 compliant with MSL Level 1.

Q: What is the difference between MMBTA42LT1G and SMMBTA42LT3G?

A: Both parts are manufactured by onsemi with identical electrical specifications: 300 V breakdown voltage, 500 mA collector current, 50 MHz transition frequency, and 225 mW power rating. The primary difference is packaging format. MMBTA42LT1G is supplied in Cut Tape (CT) & Digi-Reel format, while SMMBTA42LT3G is supplied in Tape & Reel (TR) format. Selection depends on assembly line requirements.

Q: Can FMMT497TA replace MMBTA42 in all applications?

A: FMMT497TA is suitable for most applications. It maintains the 300 V breakdown voltage and SOT-23-3 package. The 75 MHz transition frequency exceeds the original 50 MHz specification, which is beneficial for high-frequency circuits. However, verify that the 500 mW power rating is compatible with your thermal design, as it differs from the original 350 mW specification.

Q: Why is BSR19A,215 listed as a similar substitute if it has only 160 V breakdown voltage?

A: BSR19A,215 is included for reference in applications where voltage requirements are lower than 300 V. This part is not suitable for circuits designed around the 300 V specification of the MMBTA42. It is listed to prevent accidental selection in voltage-critical designs.

Q: Are all substitute parts available in the same packaging options?

A: All substitute parts are available in SOT-23-3 surface-mount packaging. However, packaging formats differ. Some parts are supplied in Cut Tape (CT) & Digi-Reel format, while others are supplied in Tape & Reel (TR) format. Verify packaging compatibility with your assembly equipment before procurement.

Q: What is the temperature range difference between MMBTA42 and its substitutes?

A: The original MMBTA42 operates from -65°C to 150°C. Most active substitutes operate from -55°C to 150°C. This represents a 10°C reduction in the lower temperature limit. For applications requiring operation below -55°C, verify that the substitute part meets your specific temperature requirements.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All substitute parts listed in this reference are ROHS3 compliant with MSL Level 1 (Unlimited) moisture sensitivity. All parts are suitable for lead-free assembly processes.

Q: Can MMBT2484LT1G be used in place of MMBTA42?

A: No. MMBT2484LT1G has a 60 V collector-emitter breakdown voltage, which is insufficient for circuits designed for 300 V operation. This part is not suitable for direct substitution and is included only for reference in low-voltage applications.

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