MMBT5550 Equivalent & Substitute Parts

Part Overview

The MMBT5550 is an NPN bipolar junction transistor manufactured by onsemi, housed in a SOT-23-3 surface mount package. This device is rated for 140 V collector-emitter breakdown voltage and 600 mA maximum collector current, with a maximum power dissipation of 350 mW. The MMBT5550 is classified as obsolete, necessitating identification of active equivalent and substitute components for new designs and production applications. Substitute parts must maintain electrical compatibility within the specified parameter ranges while offering active product status and current manufacturing availability.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	140	V
Current - Collector (Ic) (Max)	600	mA
Power - Max	350	mW
Vce Saturation (Max) @ Ib, Ic	250 mV @ 5 mA, 50 mA	—
DC Current Gain (hFE) (Min) @ Ic, Vce	60 @ 10 mA, 5 V	—
Current - Collector Cutoff (Max)	100	nA
Operating Temperature Range	-55 to 150	°C
Mounting Type	Surface Mount	—
Package / Case	SOT-23-3 (TO-236-3, SC-59)	—

Substitute Part Grouping Explanation

Substitution of the MMBT5550 is determined by the following critical electrical and mechanical parameters:

Primary Substitution Criteria:

Transistor Type: NPN (required match)
Voltage - Collector Emitter Breakdown (Max): minimum 140 V (equal or higher acceptable)
Current - Collector (Ic) (Max): minimum 600 mA (equal or higher acceptable)
Package / Case: SOT-23-3 surface mount (required match)
Operating Temperature Range: -55°C to 150°C (required match)

Secondary Compatibility Parameters:

Vce Saturation: 250 mV or lower at specified conditions
DC Current Gain (hFE): 60 or higher at 10 mA, 5 V
Current - Collector Cutoff (Max): 100 nA or lower

Substitute parts are grouped into two categories:

Direct Equivalents (Same Base Product Number): MMBT5550LT1G and MMBT5550LT3G maintain identical electrical specifications with reduced maximum power dissipation (225 mW vs. 350 mW) and active product status. These differ only in packaging format (Cut Tape vs. Tape & Reel).

Functional Equivalents (Higher Voltage Rating): MMBT5551LT1G, MMBT5551LT3G, SMMBT5551LT1G, and SMMBT5551LT3G provide 160 V breakdown voltage (exceeding the 140 V requirement) with identical current ratings and active status. These are suitable for applications where higher voltage margin is beneficial.

Cross-Manufacturer Alternatives: BSR19A,215 (Nexperia) and CMPT5551 TR PBFREE (Central Semiconductor) offer 160 V ratings with 300 mA and 600 mA collector current respectively, both in SOT-23-3 packages with active status.

Higher Current Capability: FMMT455TA (Diodes Incorporated) provides 1 A collector current at 140 V with 500 mW power rating, suitable for applications requiring increased current handling.

Parameter Comparison

Part Number	Manufacturer	Product Status	Ic (Max) mA	Vce(br) (Max) V	Power (Max) mW	Vce Sat (Max) mV	hFE (Min)	Package	RoHS Status
MMBT5550	onsemi	Obsolete	600	140	350	250	60	SOT-23-3	—
MMBT5550LT1G	onsemi	Active	600	140	225	250	60	SOT-23-3	ROHS3
MMBT5550LT3G	onsemi	Active	600	140	225	250	60	SOT-23-3	ROHS3
MMBT5551LT1G	onsemi	Active	600	160	225	200	80	SOT-23-3	ROHS3
MMBT5551LT3G	onsemi	Active	600	160	225	200	80	SOT-23-3	ROHS3
SMMBT5551LT1G	onsemi	Active	600	160	225	200	80	SOT-23-3	ROHS3
SMMBT5551LT3G	onsemi	Active	600	160	225	200	80	SOT-23-3	ROHS3
BSR19A,215	Nexperia USA Inc.	Active	300	160	250	150	80	TO-236AB	ROHS3
CMPT5551 TR PBFREE	Central Semiconductor Corp	Active	600	160	350	200	80	SOT-23	ROHS3
FMMT455TA	Diodes Incorporated	Active	1000	140	500	700	100	SOT-23-3	ROHS3

Engineering Selection Recommendations

For Direct Replacement (Identical Electrical Performance):

MMBT5550LT1G and MMBT5550LT3G are the primary substitutes for the obsolete MMBT5550. Both maintain the same base product number, electrical specifications, and SOT-23-3 package. The distinction between these parts is packaging format: MMBT5550LT1G is supplied in Cut Tape (CT) & Digi-Reel® format with 605,400 units in stock, while MMBT5550LT3G is supplied in Tape & Reel (TR) format with 10,237 units in stock. Both are ROHS3 compliant and carry active product status. Selection between these two should be based on procurement and assembly line requirements.

For Applications Requiring Voltage Margin:

MMBT5551LT1G, MMBT5551LT3G, SMMBT5551LT1G, and SMMBT5551LT3G provide 160 V breakdown voltage, exceeding the MMBT5550 specification by 20 V. These parts maintain 600 mA collector current and are suitable for designs where higher voltage headroom is advantageous. MMBT5551LT1G offers the highest inventory (1,304,400 units) and is available in Cut Tape format. All variants are ROHS3 compliant with active status.

For Cross-Manufacturer Sourcing:

CMPT5551 TR PBFREE (Central Semiconductor Corp) provides electrical equivalence with 160 V rating, 600 mA current, and 350 mW power dissipation matching the original MMBT5550 power rating. This part is ROHS3 compliant and active, with 6,299 units in stock.

For Higher Current Applications:

FMMT455TA (Diodes Incorporated) is suitable only for applications where 1 A collector current is required. This part maintains 140 V breakdown voltage but exhibits higher Vce saturation (700 mV vs. 250 mV), making it unsuitable as a direct replacement in current-limited designs.

Not Recommended:

BSR19A,215 (Nexperia) is limited to 300 mA maximum collector current, which is insufficient for the MMBT5550 specification of 600 mA. This part is suitable only for applications with reduced current requirements.

Frequently Asked Questions (FAQ)

Q: Can MMBT5550LT1G and MMBT5550LT3G be used interchangeably with the obsolete MMBT5550?

A: Yes. Both parts are direct electrical equivalents with identical specifications for collector current (600 mA), breakdown voltage (140 V), saturation voltage (250 mV), and current gain (hFE 60 minimum). The only differences are packaging format (Cut Tape vs. Tape & Reel) and inventory levels. Selection should be based on assembly line compatibility and procurement requirements.

Q: What is the difference between MMBT5551 and MMBT5550 variants?

A: The MMBT5551 series provides 160 V collector-emitter breakdown voltage compared to 140 V for MMBT5550. Both maintain 600 mA collector current. The MMBT5551 also exhibits lower saturation voltage (200 mV vs. 250 mV) and higher current gain (hFE 80 vs. 60). These differences make MMBT5551 suitable for applications requiring higher voltage margins or improved switching characteristics.

Q: Are MMBT5551LT1G and SMMBT5551LT1G electrically identical?

A: Yes. Both parts share identical electrical specifications: 160 V breakdown voltage, 600 mA collector current, 225 mW power dissipation, 200 mV saturation voltage, and hFE 80 minimum. The "S" prefix in SMMBT5551 indicates a different manufacturing line or qualification level, but electrical performance is equivalent. Selection should be based on availability and procurement preferences.

Q: Can FMMT455TA replace MMBT5550 in all applications?

A: No. While FMMT455TA maintains the same 140 V breakdown voltage and SOT-23-3 package, it is rated for 1 A collector current (vs. 600 mA) and exhibits significantly higher saturation voltage (700 mV vs. 250 mV). This higher saturation voltage makes FMMT455TA unsuitable for applications sensitive to saturation characteristics. Use FMMT455TA only in applications specifically requiring 1 A current capability.

Q: Is BSR19A,215 a suitable substitute for MMBT5550?

A: No. BSR19A,215 is limited to 300 mA maximum collector current, which is 50% below the MMBT5550 specification of 600 mA. This part is suitable only for applications with reduced current requirements. For full 600 mA capability, use MMBT5550LT1G, MMBT5550LT3G, or MMBT5551 variants.

Q: What is the significance of the "LT1G" and "LT3G" suffixes in onsemi part numbers?

A: These suffixes indicate packaging and tape format. "LT1G" denotes Cut Tape (CT) & Digi-Reel® packaging, suitable for automated pick-and-place assembly from reel format. "LT3G" denotes standard Tape & Reel (TR) packaging. Electrical specifications are identical; selection depends on assembly equipment compatibility and procurement format preferences.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All active substitute parts listed (MMBT5550LT1G, MMBT5550LT3G, MMBT5551 variants, SMMBT5551 variants, BSR19A,215, CMPT5551 TR PBFREE, and FMMT455TA) are ROHS3 compliant. The original MMBT5550 does not specify RoHS status due to its obsolete classification.

Q: What is the operating temperature range for all substitute parts?

A: All substitute parts operate across -55°C to 150°C junction temperature range, matching the original MMBT5550 specification. This ensures thermal compatibility in existing designs without modification.

Q: Can CMPT5551 TR PBFREE be used as a direct replacement for MMBT5550?

A: CMPT5551 TR PBFREE is functionally equivalent with 160 V breakdown voltage, 600 mA collector current, and 350 mW power dissipation. However, the package designation differs slightly (SOT-23 vs. SOT-23-3), though both are physically compatible in TO-236-3 footprints. Verify PCB footprint compatibility before selection. This part is manufactured by Central Semiconductor Corp and is ROHS3 compliant.

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