MMBTA55-7 Equivalent & Substitute Parts

Part Overview

The MMBTA55-7 is a PNP bipolar junction transistor manufactured by Diodes Incorporated, rated for 60 V collector-emitter breakdown voltage and 500 mA maximum collector current. The device is packaged in SOT-23-3 surface mount configuration and qualified to AEC-Q101 automotive standards. This part is discontinued at DiGi Electronics, necessitating identification of functionally equivalent alternatives that maintain electrical and mechanical compatibility within specified parameter ranges.

Key Parameters

Parameter	Value	Unit
Transistor Type	PNP	—
Collector Current (Max)	500	mA
Collector-Emitter Breakdown Voltage (Max)	60	V
Power Dissipation (Max)	300	mW
Transition Frequency	50	MHz
Operating Temperature Range	−55 to 150	°C
Package Type	SOT-23-3	—
Mounting Type	Surface Mount	—
Grade	Automotive	—
Qualification	AEC-Q101	—

Substitute Part Grouping Explanation

Substitution of the MMBTA55-7 is determined by the following critical parameters:

Mandatory Compatibility Criteria:

Transistor type must be PNP
Collector current rating must be ≥500 mA
Collector-emitter breakdown voltage must be ≥60 V
Package must be SOT-23-3 or equivalent surface mount configuration
Mounting type must be surface mount

Acceptable Variation Parameters:

Power dissipation may be ≥300 mW
Transition frequency may exceed 50 MHz
Operating temperature range may equal or exceed −55 to 150 °C
DC current gain (hFE) may vary within device specifications
Vce saturation characteristics may differ within acceptable operating ranges

Substitute parts are grouped into two categories: direct equivalents from the original manufacturer (Diodes Incorporated) with identical electrical specifications, and cross-manufacturer alternatives that meet or exceed the minimum electrical requirements while maintaining package and mounting compatibility.

Parameter Comparison

Part Number	Manufacturer	Ic (Max) [mA]	Vce(br) (Max) [V]	Power (Max) [mW]	Frequency [MHz]	Package	Status	RoHS
MMBTA55-7	Diodes Incorporated	500	60	300	50	SOT-23-3	Discontinued	Non-compliant
MMBTA55-7-F	Diodes Incorporated	500	60	300	50	SOT-23-3	Active	RoHS3 Compliant
MMBTA55LT1G	onsemi	500	60	225	50	SOT-23-3	Active	RoHS3 Compliant
2PB710ARL,215	Nexperia USA Inc.	500	50	250	120	TO-236AB	Active	RoHS3 Compliant
2SA1313-Y,LF	Toshiba Semiconductor and Storage	500	50	200	200	S-Mini	Active	RoHS3 Compliant
BC807-40,215	Nexperia USA Inc.	500	45	250	80	TO-236AB	Active	RoHS3 Compliant
BC807K-16R	Nexperia USA Inc.	500	45	250	80	TO-236AB	Active	RoHS3 Compliant
BC807K-25VL	Nexperia USA Inc.	500	45	250	80	TO-236AB	Active	RoHS3 Compliant
BCX17,215	Nexperia USA Inc.	500	45	250	80	TO-236AB	Active	RoHS3 Compliant
BCX17,235	NXP USA Inc.	500	45	250	80	SOT-23	Active	Not specified
BCX17LT1G	onsemi	500	45	300	Not specified	SOT-23-3	Active	RoHS3 Compliant

Engineering Selection Recommendations

Tier 1 — Direct Manufacturer Replacement:

MMBTA55-7-F from Diodes Incorporated is the primary substitute. This part maintains identical electrical specifications to the original MMBTA55-7 while offering active product status and RoHS3 compliance. The only difference is packaging format (Tape & Reel versus cut tape), which does not affect electrical performance or board-level compatibility.

Tier 2 — Equivalent Electrical Performance, Active Status:

MMBTA55LT1G from onsemi provides identical voltage and current ratings with the same 50 MHz transition frequency. Power dissipation is reduced to 225 mW, which is acceptable for applications not requiring the full 300 mW rating. This part carries AEC-Q101 qualification and RoHS3 compliance.

Tier 3 — Reduced Voltage Rating, Enhanced Frequency:

Parts in this category (2PB710ARL,215, 2SA1313-Y,LF, BC807-40,215, BC807K-16R, BC807K-25VL, BCX17,215, BCX17,235, BCX17LT1G) feature collector-emitter breakdown voltages of 45 V or 50 V, which are below the original 60 V specification. These substitutes are suitable only for applications where the circuit design operates at voltages not exceeding the reduced rating. All maintain 500 mA collector current capability and surface mount SOT-23-3 or equivalent packaging. Most carry AEC-Q101 or AEC-Q100 automotive qualification.

Compliance Considerations:

All active substitute parts listed are RoHS3 compliant, addressing environmental regulatory requirements. The original MMBTA55-7 is RoHS non-compliant; migration to compliant alternatives is recommended for new designs and long-term supply chain stability.

Frequently Asked Questions (FAQ)

Q: Can MMBTA55-7-F be used as a direct replacement for MMBTA55-7?

A: Yes. MMBTA55-7-F is manufactured by Diodes Incorporated and maintains identical electrical specifications: 60 V breakdown voltage, 500 mA collector current, 300 mW power dissipation, and 50 MHz transition frequency. The difference is packaging format (Tape & Reel). Both use SOT-23-3 surface mount configuration.

Q: What is the key limitation when substituting BC807 series parts?

A: BC807 series transistors (BC807-40,215, BC807K-16R, BC807K-25VL) have a maximum collector-emitter breakdown voltage of 45 V, compared to 60 V for the MMBTA55-7. These substitutes are suitable only for circuits designed to operate below 45 V. All other electrical parameters (500 mA current, surface mount packaging) remain compatible.

Q: Are BCX17 variants suitable replacements?

A: BCX17 variants (BCX17,215, BCX17,235, BCX17LT1G) meet the 500 mA collector current requirement and use compatible SOT-23-3 packaging. However, they feature a 45 V breakdown voltage rating, requiring circuit voltage verification. BCX17LT1G from onsemi offers 300 mW power dissipation matching the original specification.

Q: What is the difference between MMBTA55LT1G and MMBTA55-7?

A: MMBTA55LT1G from onsemi maintains the 60 V breakdown voltage and 500 mA current rating. Power dissipation is 225 mW versus 300 mW in the original. This reduction does not affect functionality in standard applications. Both use SOT-23-3 packaging and support −55 to 150 °C operating temperature.

Q: Why do some substitutes have higher transition frequencies?

A: Transition frequency (fT) indicates the frequency at which transistor gain begins to roll off. Higher frequencies (120 MHz, 200 MHz) represent enhanced high-frequency performance. These parts remain backward compatible with applications designed for 50 MHz operation, as they exceed the original specification.

Q: Is automotive qualification important for substitution?

A: Automotive qualification (AEC-Q101 or AEC-Q100) indicates the part meets automotive reliability and quality standards. The original MMBTA55-7 carries AEC-Q101 qualification. Most active substitutes maintain this or equivalent qualification, ensuring consistent reliability in automotive applications.

Q: Can parts with different package designations (TO-236AB versus SOT-23-3) be interchanged?

A: TO-236AB and SOT-23-3 are equivalent package designations for the same physical form factor. Both refer to a three-lead surface mount package with identical pin spacing and dimensions. These designations are interchangeable at the board level.

Q: What should be considered when selecting between Tier 2 and Tier 3 substitutes?

A: Tier 2 substitutes (MMBTA55LT1G) maintain the 60 V voltage rating, making them suitable for any circuit originally designed for MMBTA55-7. Tier 3 substitutes require circuit voltage verification to ensure operation remains below their 45 V or 50 V ratings. If circuit voltage exceeds the substitute's rating, Tier 2 is the appropriate choice.

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