MMBTA28 Equivalent & Substitute Parts

Part Overview

The MMBTA28 is an NPN Darlington bipolar junction transistor manufactured by onsemi, designed for surface mount applications in the SOT-23-3 package. This device operates at a maximum collector voltage of 80 V with a collector current rating of 800 mA and a maximum power dissipation of 350 mW. The part is currently in active production status with extensive inventory availability. Substitute parts are identified when equivalent electrical performance can be achieved within the specified parameter ranges while maintaining compatibility with the application circuit requirements.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN - Darlington	—
Collector Current (Max)	800	mA
Collector-Emitter Breakdown Voltage (Max)	80	V
Vce Saturation (Max)	1.5	V @ 100µA, 100mA
DC Current Gain (hFE Min)	10000	@ 100mA, 5V
Power Dissipation (Max)	350	mW
Transition Frequency	125	MHz
Operating Temperature Range	-55 to 150	°C (TJ)
Package Type	SOT-23-3	—
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitution of the MMBTA28 is determined by the following critical electrical and mechanical parameters:

Voltage Rating: All substitute parts must maintain the 80 V collector-emitter breakdown voltage specification to ensure safe operation in the target circuit.

Transistor Type: All substitutes must be NPN Darlington configuration to preserve the high current gain characteristic essential for Darlington applications.

Package Compatibility: The primary substitute MMBTA28-7-F maintains the SOT-23-3 package for direct pin-compatible replacement. The secondary substitute BSP52T1G uses the SOT-223 package, requiring circuit board layout modification.

Current Rating: The MMBTA28 specifies 800 mA maximum collector current. Substitutes with equal or higher current ratings (500 mA minimum for reduced-current applications, 1 A for higher-current applications) are acceptable based on circuit requirements.

Power Dissipation: Maximum power rating of 350 mW for the MMBTA28 establishes the thermal design envelope. Substitutes with equal or higher power ratings are acceptable.

DC Current Gain: The minimum hFE of 10000 at specified conditions is a defining characteristic. Substitutes with hFE values meeting or exceeding this specification maintain equivalent switching performance.

Compliance: All substitute parts must maintain ROHS3 compliance and active product status.

Parameter Comparison

Parameter	MMBTA28 (onsemi)	MMBTA28-7-F (Diodes Inc.)	BSP52T1G (onsemi)
Transistor Type	NPN - Darlington	NPN - Darlington	NPN - Darlington
Collector Current (Max)	800 mA	500 mA	1 A
Collector-Emitter Breakdown Voltage (Max)	80 V	80 V	80 V
Vce Saturation (Max)	1.5 V @ 100µA, 100mA	1.5 V @ 100µA, 100mA	1.3 V @ 500µA, 500mA
DC Current Gain (hFE Min)	10000 @ 100mA, 5V	10000 @ 100mA, 5V	2000 @ 500mA, 10V
Power Dissipation (Max)	350 mW	300 mW	800 mW
Transition Frequency	125 MHz	125 MHz	Not specified
Operating Temperature Range	-55 to 150 °C	-55 to 150 °C	-65 to 150 °C
Package Type	SOT-23-3	SOT-23-3	SOT-223
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Product Status	Active	Active	Active

Engineering Selection Recommendations

MMBTA28-7-F (Diodes Incorporated): This part provides direct SOT-23-3 package compatibility with the MMBTA28, enabling pin-for-pin replacement without circuit board modification. The MMBTA28-7-F maintains identical voltage rating, saturation voltage, and DC current gain specifications. The reduced collector current rating of 500 mA is suitable for applications where the circuit current demand does not exceed this threshold. This part carries AEC-Q101 automotive qualification, providing additional reliability assurance for automotive-grade applications. All compliance certifications (ROHS3, REACH Unaffected) match the original part.

BSP52T1G (onsemi): This part offers higher current capacity at 1 A maximum collector current and increased power dissipation capability at 800 mW, suitable for applications requiring greater thermal headroom or higher current switching. The SOT-223 package requires circuit board layout redesign and is not pin-compatible with the MMBTA28. The DC current gain specification of 2000 at 500 mA, 10V is lower than the MMBTA28 specification, which may affect switching speed in applications dependent on high current gain. The extended operating temperature range to -65°C provides additional low-temperature margin. This part maintains onsemi manufacturing and ROHS3 compliance.

Selection between substitutes depends on circuit current requirements, available board space, and thermal design constraints. Direct replacement applications favor MMBTA28-7-F. Higher-current or higher-power applications favor BSP52T1G with corresponding layout modifications.

Frequently Asked Questions (FAQ)

Q: Can MMBTA28-7-F replace MMBTA28 without circuit modification?

A: Yes. MMBTA28-7-F is pin-compatible in the SOT-23-3 package and maintains the same voltage rating, saturation voltage, and DC current gain. No circuit board layout changes are required. However, the reduced collector current rating of 500 mA must not be exceeded in the application.

Q: What is the primary difference between MMBTA28 and BSP52T1G?

A: The primary differences are package type (SOT-23-3 versus SOT-223), collector current rating (800 mA versus 1 A), power dissipation (350 mW versus 800 mW), and DC current gain specification (10000 versus 2000). BSP52T1G requires circuit board redesign due to package incompatibility.

Q: Can BSP52T1G be used in place of MMBTA28 in a space-constrained application?

A: No. The SOT-223 package is larger than SOT-23-3 and may not fit in space-constrained designs. Additionally, circuit board layout modification is required for pin reassignment.

Q: Are all three parts RoHS compliant?

A: Yes. MMBTA28, MMBTA28-7-F, and BSP52T1G are all ROHS3 compliant and REACH unaffected.

Q: What is the significance of the DC current gain (hFE) difference between MMBTA28 and BSP52T1G?

A: The MMBTA28 specifies hFE minimum of 10000 at 100 mA, 5V, while BSP52T1G specifies hFE minimum of 2000 at 500 mA, 10V. The higher hFE of MMBTA28 provides greater base current efficiency and faster switching response in low-current applications. Applications sensitive to switching speed or base drive requirements should verify compatibility with the lower hFE of BSP52T1G.

Q: Can MMBTA28-7-F be used in automotive applications?

A: Yes. MMBTA28-7-F carries AEC-Q101 automotive qualification, making it suitable for automotive-grade applications. The original MMBTA28 does not specify automotive qualification.

Q: What is the operating temperature range difference?

A: MMBTA28 and MMBTA28-7-F operate from -55°C to 150°C. BSP52T1G extends the lower temperature limit to -65°C, providing additional margin for extreme cold-weather applications.

Q: Is inventory availability a factor in part selection?

A: Inventory levels are provided for reference: MMBTA28 (4036 pcs), MMBTA28-7-F (275400 pcs), and BSP52T1G (64200 pcs). MMBTA28-7-F has significantly higher availability, which may influence procurement decisions for high-volume production.

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