MMBT5551 Equivalent & Substitute Parts

Part Overview

The MMBT5551 is a surface-mount NPN bipolar junction transistor manufactured by onsemi, housed in a SOT-23-3 package. This device is rated for 160 V collector-emitter breakdown voltage and 600 mA maximum collector current, with a maximum power dissipation of 350 mW. The original MMBT5551 carries an obsolete product status, making equivalent and substitute parts necessary for ongoing design support and procurement.

Substitute parts are selected based on electrical compatibility within the allowed parameter ranges for NPN transistor applications, including collector current, breakdown voltage, saturation characteristics, DC current gain, and thermal operating range.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	160	V
Current - Collector (Ic) (Max)	600	mA
Vce Saturation (Max) @ Ib, Ic	200 mV @ 5 mA, 50 mA	—
Current - Collector Cutoff (Max)	50	nA
DC Current Gain (hFE) (Min) @ Ic, Vce	80 @ 10 mA, 5 V	—
Power - Max	350	mW
Frequency - Transition	100	MHz
Operating Temperature	−55 to 150	°C
Package / Case	SOT-23-3	—
Mounting Type	Surface Mount	—

Substitute Part Grouping Explanation

Substitute parts for the MMBT5551 are classified into two categories based on electrical parameter alignment:

Direct Substitutes maintain all critical electrical parameters within the same specification envelope:

Collector-emitter breakdown voltage: 160 V
Maximum collector current: 600 mA
Saturation voltage: 200 mV @ 5 mA, 50 mA
DC current gain (hFE): 80 @ 10 mA, 5 V
Operating temperature range: −55°C to 150°C
Package: SOT-23-3 (TO-236-3, SC-59)

Similar Parts share the same package and mounting type but operate within different voltage or current specifications. These parts are suitable only when the application voltage or current requirements are lower than the original specification.

The following parameters determine substitution eligibility:

Collector-emitter breakdown voltage (must equal or exceed application requirement)
Maximum collector current (must equal or exceed application requirement)
Saturation voltage characteristics
DC current gain (hFE)
Operating temperature range
Package compatibility (SOT-23-3)

Parameter Comparison

Part Number	Manufacturer	Vce Breakdown (V)	Ic Max (mA)	Vce Sat @ 5mA, 50mA (mV)	hFE Min @ 10mA, 5V	Power Max (mW)	Frequency (MHz)	Product Status	Package
MMBT5551	onsemi	160	600	200	80	350	100	Obsolete	SOT-23-3
MMBT5551LT1G	onsemi	160	600	200	80	225	—	Active	SOT-23-3
SMMBT5551LT1G	onsemi	160	600	200	80	225	—	Active	SOT-23-3
SMMBT5551LT3G	onsemi	160	600	200	80	225	—	Active	SOT-23-3
MMBT5551LT3G	onsemi	160	600	200	80	225	—	Active	SOT-23-3
CMPT5551 TR PBFREE	Central Semiconductor Corp	160	600	200	80	350	300	Active	SOT-23-3
MMBT5551-7-F	Diodes Incorporated	160	600	200	80	300	300	Active	SOT-23-3
ZXTN5551FLTA	Diodes Incorporated	160	600	200	80	330	130	Active	SOT-23-3
MMBT5550LT1G	onsemi	140	600	250	60	225	—	Active	SOT-23-3
MMBT5550LT3G	onsemi	140	600	250	60	225	—	Active	SOT-23-3
MMBT6429LT1G	onsemi	45	200	600	500	225	700	Active	SOT-23-3

Engineering Selection Recommendations

Direct Substitutes (Recommended for MMBT5551 Replacement)

The following parts are direct electrical equivalents with active product status and full compliance certifications:

MMBT5551LT1G (onsemi): Active status, RoHS3 compliant, identical electrical specifications. Available in Cut Tape and Digi-Reel packaging.
SMMBT5551LT1G (onsemi): Active status, RoHS3 compliant, identical electrical specifications. Available in Cut Tape and Digi-Reel packaging.
SMMBT5551LT3G (onsemi): Active status, RoHS3 compliant, identical electrical specifications. Available in Tape & Reel packaging.
MMBT5551LT3G (onsemi): Active status, RoHS3 compliant, identical electrical specifications. Available in Cut Tape and Digi-Reel packaging.
CMPT5551 TR PBFREE (Central Semiconductor Corp): Active status, RoHS3 compliant, identical electrical specifications with higher transition frequency (300 MHz). Available in Tape & Reel packaging.
MMBT5551-7-F (Diodes Incorporated): Active status, RoHS3 compliant, AEC-Q101 automotive qualified, identical electrical specifications with higher transition frequency (300 MHz). Available in Cut Tape and Digi-Reel packaging.
ZXTN5551FLTA (Diodes Incorporated): Active status, RoHS3 compliant, identical electrical specifications with higher transition frequency (130 MHz). Available in Tape & Reel packaging.

Similar Parts (Application-Dependent Selection)

The following parts share the same package but operate within reduced voltage or current specifications:

MMBT5550LT1G and MMBT5550LT3G (onsemi): 140 V breakdown voltage, 600 mA collector current. Suitable only for applications requiring maximum 140 V operation. Lower DC current gain (60 vs. 80) and higher saturation voltage (250 mV vs. 200 mV).
MMBT6429LT1G (onsemi): 45 V breakdown voltage, 200 mA collector current. Suitable only for low-voltage, low-current applications. Not compatible with standard MMBT5551 applications.

Packaging Considerations

All direct substitutes maintain SOT-23-3 package compatibility. Selection between Cut Tape (CT), Digi-Reel, and Tape & Reel (TR) packaging depends on procurement and assembly requirements. Moisture sensitivity level (MSL) is 1 (Unlimited) for all listed parts.

Frequently Asked Questions (FAQ)

Q: Can MMBT5551LT1G replace MMBT5551 in all applications?

A: Yes. MMBT5551LT1G maintains identical electrical specifications for collector-emitter breakdown voltage (160 V), maximum collector current (600 mA), saturation voltage, and DC current gain. Both operate across the same temperature range (−55°C to 150°C). The primary difference is product status: MMBT5551 is obsolete while MMBT5551LT1G is active.

Q: What is the difference between MMBT5551LT1G and SMMBT5551LT1G?

A: Both parts are electrically identical with the same specifications. The difference lies in the base product number designation and potentially in manufacturing process or traceability. Both are onsemi products with active status and RoHS3 compliance. Selection between them depends on procurement availability and internal part numbering requirements.

Q: Can MMBT5550LT1G be used instead of MMBT5551?

A: MMBT5550LT1G is not a direct substitute. It operates at a lower breakdown voltage (140 V vs. 160 V) and has lower DC current gain (60 vs. 80). Use MMBT5550LT1G only if your application operates below 140 V and can tolerate the reduced current gain specification.

Q: What is the advantage of CMPT5551 TR PBFREE over MMBT5551LT1G?

A: CMPT5551 TR PBFREE maintains identical electrical specifications but offers higher transition frequency (300 MHz vs. unspecified for MMBT5551LT1G). This makes it suitable for higher-frequency switching applications. It is manufactured by Central Semiconductor Corp rather than onsemi.

Q: Is MMBT5551-7-F suitable for automotive applications?

A: Yes. MMBT5551-7-F is AEC-Q101 qualified and carries automotive grade designation. It maintains identical electrical specifications to MMBT5551 and is suitable for automotive-grade designs requiring this qualification.

Q: What packaging options are available for direct substitutes?

A: Direct substitutes are available in three packaging formats: Cut Tape (CT) & Digi-Reel, Tape & Reel (TR), and combinations thereof. All maintain SOT-23-3 package compatibility. Selection depends on assembly equipment and procurement volume requirements.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. All listed substitute parts carry RoHS3 compliance status. The original MMBT5551 is REACH Unaffected, and all substitutes maintain REACH Unaffected status.

Q: Can MMBT6429LT1G replace MMBT5551?

A: No. MMBT6429LT1G is not suitable as a replacement. It operates at significantly lower voltage (45 V vs. 160 V) and current (200 mA vs. 600 mA) ratings. Use only in applications specifically designed for low-voltage, low-current operation.

Q: What is the moisture sensitivity level for these parts?

A: All listed parts carry MSL 1 (Unlimited) rating, indicating no moisture sensitivity restrictions during storage or handling.

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