MMBTA42_D87Z Equivalent & Substitute Parts

Part Overview

The MMBTA42_D87Z is an NPN bipolar junction transistor manufactured by onsemi, housed in a SOT-23-3 surface mount package. This component is rated for 300 V collector-emitter breakdown voltage and 500 mA maximum collector current, with a maximum power dissipation of 240 mW. The part is classified as obsolete, necessitating identification of active equivalent and substitute components for new designs and ongoing production requirements. Equivalent parts maintain identical electrical and mechanical specifications, while substitute parts provide functional alternatives within defined parameter tolerances.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	300	V
Current - Collector (Ic) (Max)	500	mA
Power - Max	240	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	—
Moisture Sensitivity Level (MSL)	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution of the MMBTA42_D87Z is determined by strict adherence to the following electrical and mechanical parameters:

Critical Parameters for Direct Equivalence:

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

Parameters Allowing Variation in Substitutes:

Power - Max: May exceed 240 mW (higher power rating acceptable)
Frequency - Transition: May exceed 50 MHz (higher frequency acceptable)
Product Status: Active status preferred over obsolete
Packaging Format: Cut Tape, Tape & Reel, or Digi-Reel acceptable

Parts are classified as direct equivalents when all critical parameters match or exceed the main part specifications. Parts are classified as similar when one or more electrical parameters differ but remain within functional application ranges.

Parameter Comparison

Part Number	Manufacturer	Vce(BR)max (V)	Ic(Max) (mA)	Power (mW)	Freq (MHz)	hFE(Min)	Status	Package
MMBTA42_D87Z	onsemi	300	500	240	50	40	Obsolete	SOT-23-3
MMBTA42LT1G	onsemi	300	500	225	50	40	Active	SOT-23-3
SMMBTA42LT3G	onsemi	300	500	225	50	40	Active	SOT-23-3
MMBTA42LT3G	onsemi	300	500	225	50	40	Active	SOT-23-3
SMMBTA42LT1G	onsemi	300	500	225	50	40	Active	SOT-23-3
MMBTA42-7-F	Diodes Incorporated	300	500	300	50	40	Active	SOT-23-3
MMBT6429LT1G	onsemi	45	200	225	700	500	Active	SOT-23-3
MSD42T1G	onsemi	300	150	150	—	40	Active	SC-59
FMMT497TA	Diodes Incorporated	300	500	500	75	80	Active	SOT-23-3
FMMT6517TA	Diodes Incorporated	350	500	330	50	20	Active	SOT-23-3
FMMTA42TA	Diodes Incorporated	300	200	330	50	40	Active	SOT-23-3

Engineering Selection Recommendations

Direct Equivalent Parts (Recommended Primary Replacements):

The following parts provide direct electrical and mechanical equivalence to the MMBTA42_D87Z:

MMBTA42LT1G (onsemi): Active status, identical electrical specifications, available in Cut Tape and Digi-Reel packaging formats. RoHS3 compliant.
MMBTA42LT3G (onsemi): Active status, identical electrical specifications, available in Cut Tape and Digi-Reel packaging format. RoHS3 compliant.
SMMBTA42LT3G (onsemi): Active status, identical electrical specifications, available in Tape & Reel packaging. RoHS3 compliant.
SMMBTA42LT1G (onsemi): Active status, identical electrical specifications, includes AEC-Q101 automotive qualification. Available in Cut Tape and Digi-Reel packaging. RoHS3 compliant.
MMBTA42-7-F (Diodes Incorporated): Active status, identical electrical specifications except power rating increased to 300 mW. Available in Cut Tape and Digi-Reel packaging. RoHS3 compliant.

Alternative Substitute Parts (Application-Dependent Selection):

The following parts provide functional alternatives where specific application requirements permit parameter variation:

FMMT497TA (Diodes Incorporated): Maintains 300 V breakdown voltage and 500 mA collector current. Offers increased power dissipation (500 mW) and higher transition frequency (75 MHz). Higher DC current gain (80 vs. 40). Suitable for applications requiring enhanced frequency response or power handling.
FMMT6517TA (Diodes Incorporated): Provides higher breakdown voltage (350 V) and increased power dissipation (330 mW). Lower DC current gain (20 vs. 40) and higher saturation voltage. Suitable for higher voltage applications.
FMMTA42TA (Diodes Incorporated): Maintains 300 V breakdown voltage and 50 MHz transition frequency with identical DC current gain. Reduced collector current rating (200 mA vs. 500 mA). Suitable for lower current applications.
MSD42T1G (onsemi): Maintains 300 V breakdown voltage and identical DC current gain. Reduced collector current (150 mA) and power dissipation (150 mW). Packaged in SC-59 variant. Suitable for lower current applications.
MMBT6429LT1G (onsemi): Not recommended as primary substitute. Significantly reduced breakdown voltage (45 V) and collector current (200 mA) with substantially different DC current gain (500 vs. 40). Suitable only for low-voltage applications.

Compliance and Certification Status:

All recommended direct equivalent parts maintain RoHS3 compliance and REACH unaffected status. SMMBTA42LT1G includes AEC-Q101 automotive qualification for applications requiring automotive-grade components. All parts carry MSL 1 (Unlimited) moisture sensitivity rating.

Frequently Asked Questions (FAQ)

Q: Can MMBTA42LT1G directly replace MMBTA42_D87Z in existing designs?

A: Yes. MMBTA42LT1G provides direct electrical and mechanical equivalence. Both components share identical voltage ratings (300 V), current ratings (500 mA), DC current gain specifications (40 @ 30mA, 10V), and saturation voltage characteristics. Both are packaged in SOT-23-3. The primary difference is product status: MMBTA42_D87Z is obsolete while MMBTA42LT1G is active. Packaging format may differ (Cut Tape vs. original format), but this does not affect electrical performance.

Q: What is the difference between MMBTA42LT1G, MMBTA42LT3G, SMMBTA42LT3G, and SMMBTA42LT1G?

A: All four parts share identical electrical specifications. Differences are in packaging format and qualification level. MMBTA42LT1G and MMBTA42LT3G are available in Cut Tape and Digi-Reel formats. SMMBTA42LT3G is supplied in Tape & Reel format. SMMBTA42LT1G is supplied in Cut Tape and Digi-Reel format and includes AEC-Q101 automotive qualification. Selection depends on packaging requirements and whether automotive-grade qualification is necessary.

Q: Why is MMBTA42-7-F (Diodes Incorporated) listed as a substitute?

A: MMBTA42-7-F maintains all critical electrical parameters: 300 V breakdown voltage, 500 mA collector current, 50 MHz transition frequency, and 40 DC current gain. The power rating is increased to 300 mW (vs. 240 mW), which is acceptable as a higher rating does not compromise functionality. This part is manufactured by Diodes Incorporated rather than onsemi, providing an alternative source for the same functional specification.

Q: Can FMMT497TA replace MMBTA42_D87Z?

A: FMMT497TA is a functional alternative, not a direct equivalent. It maintains the same 300 V breakdown voltage and 500 mA collector current. However, it offers higher transition frequency (75 MHz vs. 50 MHz), higher power dissipation (500 mW vs. 240 mW), and higher DC current gain (80 vs. 40). Use FMMT497TA only in applications where these enhanced specifications are beneficial or where the original part specifications are not critical.

Q: What does "SOT-23-3" packaging mean, and are all listed parts compatible?

A: SOT-23-3 is a surface mount package designation also known as TO-236-3 or SC-59. All recommended direct equivalent parts use SOT-23-3 packaging, ensuring mechanical and thermal compatibility. MSD42T1G uses the SC-59 variant, which is mechanically identical. Packaging format (Cut Tape, Tape & Reel, Digi-Reel) refers to how components are supplied, not the physical package itself, and does not affect circuit compatibility.

Q: Is SMMBTA42LT1G suitable for automotive applications?

A: Yes. SMMBTA42LT1G carries AEC-Q101 automotive qualification, indicating compliance with automotive industry reliability and quality standards. This part is suitable for automotive applications requiring qualified components. Other onsemi MMBTA42 variants (MMBTA42LT1G, MMBTA42LT3G, SMMBTA42LT3G) do not carry automotive qualification and should not be used in applications requiring AEC-Q101 compliance.

Q: Why is MMBT6429LT1G not recommended as a substitute?

A: MMBT6429LT1G differs significantly in critical parameters. It provides only 45 V breakdown voltage (vs. 300 V), 200 mA collector current (vs. 500 mA), and 700 MHz transition frequency with 500 DC current gain (vs. 40). These specifications are suitable only for low-voltage, high-frequency applications. Use MMBT6429LT1G only if your application operates at 45 V or lower and requires higher frequency response.

Q: What is the significance of "RoHS3 Compliant" status?

A: RoHS3 compliance indicates the component meets Restriction of Hazardous Substances Directive requirements, restricting use of lead and other hazardous materials. All recommended active substitute parts carry RoHS3 compliance, making them suitable for applications subject to environmental regulations. The obsolete MMBTA42_D87Z does not list RoHS3 status.

Q: Can I use MSD42T1G as a substitute for lower current applications?

A: MSD42T1G is suitable only for applications where collector current does not exceed 150 mA. It maintains the same 300 V breakdown voltage and 40 DC current gain as the original part. If your circuit requires the full 500 mA capability, MSD42T1G is not appropriate. Use MSD42T1G only after confirming that actual circuit current requirements are below 150 mA.

Q: What does "Moisture Sensitivity Level (MSL) 1 (Unlimited)" mean?

A: MSL 1 indicates the component has unlimited shelf life and does not require special moisture control during storage or handling. This is the least restrictive moisture sensitivity rating. All listed parts carry MSL 1, meaning they can be stored and handled under standard conditions without special precautions or baking procedures before soldering.

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