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Home > Products > Discrete Semiconductor Products > Transistors > Bipolar (BJT) > Single Bipolar Transistors

onsemi MMBTA28

Name: MMBTA28
Brand: onsemi
SKU: MMBTA28
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: MMBTA28

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-236-3, SC-59, SOT-23-3

Datasheet:: MMBTA28.pdf

Description:: TRANS NPN DARL 80V 0.8A SOT-23-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

MMBTA28 from onsemi is an NPN Darlington transistor in SOT-23 package, designed for high-current-gain switching and amplification up to 800 mA collector current, with V_CEO = 80 V, h_FE ≥ 10,000 at I_C = 10–100 mA, and f_T = 125 MHz - used in low-power relay drivers and sensor interface stages.

For engineers reviewing the MMBTA28 datasheet, pinout, applications, or equivalent options, key selection criteria include its Darlington architecture for high DC gain, SOT-23 thermal limitations (P_D = 350 mW), V_BE(on) = 2.0 V at I_C = 100 mA, and AEC-Q101 qualification for automotive-grade reliability validation.

Technical Context

The MMBTA28 implements a monolithic NPN Darlington pair with integrated base-emitter resistor network, enabling single-base control of high current gain while maintaining stable bias under temperature variation. Its structure delivers h_FE ≥ 10,000 across I_C = 10–100 mA and V_CE = 5 V, with V_CE(sat) ≤ 1.5 V at I_C = 100 mA / I_B = 0.1 mA.

It operates within −55 °C to +150 °C junction temperature range and supports pulsed operation per Note 5 (pulse width ≤ 300 µs, duty cycle ≤ 2.0%). Thermal resistance R_JA = 357 °C/W reflects its SOT-23 mounting constraints on 36 mm × 18 mm FR-4 PCB with 6 cm² collector pad.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	80 V - maximum safe collector-emitter voltage before breakdown; enables use in 24 V industrial control rails with margin.
I_C (continuous)	800 mA - continuous collector current rating; suitable for driving small relays or LED arrays without forced cooling.
h_FE	≥10,000 at I_C = 10–100 mA - ultra-high DC current gain reduces required base drive current, easing microcontroller GPIO loading.
f_T	125 MHz - unity-gain bandwidth; supports signal amplification up to low-MHz analog sensing front-ends.
P_D	350 mW at T_A = 25 °C - power dissipation limit in SOT-23; requires derating by 2.8 mW/°C above ambient.
V_BE(on)	2.0 V at I_C = 100 mA - forward base-emitter voltage; impacts minimum logic-high level needed for full saturation.
C_obo	8.0 pF at V_CB = 1.0 V - output capacitance; limits high-frequency switching speed and affects EMI in fast-switching applications.

Pinout & Package

MMBTA28 is housed in a 3-lead SOT-23 (Case 527AG) surface-mount package with standard lead configuration: emitter (E), base (B), and collector (C) assigned to pins 1, 2, and 3 respectively per JEDEC MO-178AB outline.

Pin/Terminal	Circuit Role	Design Meaning
Pin 1 (Emitter)	Emitter terminal of Darlington pair	Reference node for base drive; connects to ground or low-side return path in common-emitter configurations.
Pin 2 (Base)	Control input for Darlington pair	Accepts low-current logic-level signal; internal resistor network simplifies external biasing requirements.
Pin 3 (Collector)	High-current output node	Drives load between V_CC and collector; requires thermal pad area ≥6 cm² on PCB for rated power handling.

Key Features

Feature	Design Value
AEC-Q101 qualified	Validated for automotive applications including engine control modules and body electronics requiring extended temperature and reliability compliance.
Pb-free construction	Meets RoHS Directive 2011/65/EU and JESD204B material restrictions; compatible with lead-free reflow soldering profiles.
Darlington architecture	Delivers h_FE ≥ 10,000 without external feedback components, reducing board space and component count in high-gain amplifier stages.
Low V_CE(sat)	1.2 V at I_C = 10 mA / I_B = 0.01 mA - minimizes conduction loss in battery-powered switch-mode circuits.
Wide T_J range	−55 °C to +150 °C - supports deployment in under-hood automotive, industrial motor controls, and outdoor IoT sensor nodes.

Applications

Relay Driver Circuit	Automotive Door Lock Actuator
Use Scenario: Driving 12 V, 200 mA coil relays from MCU GPIO pins with limited current sourcing capability. IC Role / Device Role / Timing Role: High-gain Darlington switch providing isolation and current amplification between logic-level control and inductive load. Use Value: Eliminates need for discrete base resistors or dual-transistor stages; achieves full saturation with <10 µA base current due to h_FE ≥ 10,000.	Use Scenario: Controlling solenoid-based door lock actuators in passenger vehicles under varying ambient temperatures. IC Role / Device Role / Timing Role: Robust switching element in body control module (BCM) output stage, interfacing with LIN bus-controlled logic. Use Value: AEC-Q101 qualification ensures operation across −40 °C to +125 °C ambient, with V_CEO = 80 V accommodating load dump transients.
Industrial Sensor Signal Conditioning	Low-Power LED Array Driver
Use Scenario: Amplifying weak current-mode outputs from photodiode or thermopile sensors before ADC sampling. IC Role / Device Role / Timing Role: Transimpedance amplifier front-end stage using Darlington configuration for ultra-low input bias current. Use Value: ICBO ≤ 100 nA and h_FE ≥ 10,000 enable accurate DC-coupled amplification of sub-µA sensor currents without significant error.	Use Scenario: Switching 5–10 white LEDs (total ~350 mA) in portable medical devices powered by single-cell Li-ion batteries. IC Role / Device Role / Timing Role: Low-saturation switch in constant-current LED driver topology with PWM dimming input. Use Value: V_CE(sat) ≤ 1.5 V at 100 mA reduces power loss and thermal rise, extending battery runtime and enabling compact PCB layout.

Relay Driver Circuit

Automotive Door Lock Actuator

Use Scenario: Driving 12 V, 200 mA coil relays from MCU GPIO pins with limited current sourcing capability.

IC Role / Device Role / Timing Role: High-gain Darlington switch providing isolation and current amplification between logic-level control and inductive load.

Use Value: Eliminates need for discrete base resistors or dual-transistor stages; achieves full saturation with <10 µA base current due to h_FE ≥ 10,000.

Use Scenario: Controlling solenoid-based door lock actuators in passenger vehicles under varying ambient temperatures.

IC Role / Device Role / Timing Role: Robust switching element in body control module (BCM) output stage, interfacing with LIN bus-controlled logic.

Use Value: AEC-Q101 qualification ensures operation across −40 °C to +125 °C ambient, with V_CEO = 80 V accommodating load dump transients.

Industrial Sensor Signal Conditioning

Low-Power LED Array Driver

Use Scenario: Amplifying weak current-mode outputs from photodiode or thermopile sensors before ADC sampling.

IC Role / Device Role / Timing Role: Transimpedance amplifier front-end stage using Darlington configuration for ultra-low input bias current.

Use Value: ICBO ≤ 100 nA and h_FE ≥ 10,000 enable accurate DC-coupled amplification of sub-µA sensor currents without significant error.

Use Scenario: Switching 5–10 white LEDs (total ~350 mA) in portable medical devices powered by single-cell Li-ion batteries.

IC Role / Device Role / Timing Role: Low-saturation switch in constant-current LED driver topology with PWM dimming input.

Use Value: V_CE(sat) ≤ 1.5 V at 100 mA reduces power loss and thermal rise, extending battery runtime and enabling compact PCB layout.

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN Darlington transistor applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
MMBT6427	h_FE = 5000–15,000 (lower min), V_CEO = 60 V, P_D = 310 mW, same SOT-23 package	Lower voltage rating limits use in 48 V systems; reduced thermal margin at high I_C	Select when cost sensitivity outweighs need for 80 V margin and 10,000 minimum h_FE.
ZTX1048	h_FE = 10,000–30,000, V_CEO = 80 V, but TO-92 package (through-hole), P_D = 1 W	Requires through-hole assembly; higher power handling but incompatible with SMT-only production lines	Choose for prototyping or legacy through-hole designs needing identical electrical specs with greater thermal headroom.

Compared with MMBTA28, MMBT6427 offers lower cost but reduced voltage and thermal margins, while ZTX1048 matches key electrical specs but mandates through-hole assembly - making MMBTA28 optimal for SMT-based automotive and industrial designs demanding AEC-Q101 compliance and 80 V robustness.

Availability

MMBTA28 is available at Aetrix Electronics and suitable for automotive body electronics, industrial relay interfaces, and portable sensor signal conditioning requiring stable component supply and long-term lifecycle support.

Supply support for MMBTA28 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

onsemi (formerly ON Semiconductor) is a global semiconductor supplier specializing in energy-efficient power management, analog, and sensor solutions for automotive, industrial, and cloud infrastructure markets.

The MMBTA28 belongs to onsemi's general-purpose bipolar transistor product line, engineered for high-reliability discrete switching and amplification in space-constrained, thermally demanding environments.

FAQ

What is the maximum collector current rating for the MMBTA28?

The MMBTA28 has a continuous collector current rating of 800 mA at T_A = 25 °C. This rating assumes proper PCB thermal management - specifically a 6 cm² copper pad for the collector lead on FR-4 material. At elevated ambient temperatures, current must be derated per the 2.8 mW/°C thermal coefficient to maintain junction temperature below 150 °C. The MMBTA28 datasheet confirms this value under Absolute Maximum Ratings.

Is the MMBTA28 suitable for automotive applications?

Yes, the MMBTA28 is AEC-Q101 qualified and PPAP capable, making it suitable for automotive applications such as door lock actuators, lighting controls, and body electronics. It operates across −55 °C to +150 °C junction temperature and meets stringent reliability requirements for automotive-grade components. The MMBTA28 also carries NSV prefix variants for enhanced traceability in automotive supply chains.

What is the typical DC current gain (h_FE) of the MMBTA28?

The MMBTA28 guarantees h_FE ≥ 10,000 at both I_C = 10 mA and I_C = 100 mA with V_CE = 5.0 V. This ultra-high gain is inherent to its monolithic Darlington structure and enables minimal base drive current - often less than 10 µA for full saturation at 100 mA collector load. The MMBTA28 datasheet specifies this performance under Electrical Characteristics.

Does the MMBTA28 have Pb-free packaging?

Yes, the MMBTA28 is manufactured as a Pb-free device compliant with RoHS Directive 2011/65/EU. Its SOT-23 package uses lead-free terminations and conforms to JESD204B material standards. The "G" suffix in part numbers like NSVMMBTA28LT1G explicitly denotes Pb-free construction, and the MMBTA28 itself is supplied in Pb-free tape-and-reel format per ordering information.

What is the thermal resistance (R_JA) of the MMBTA28 in its SOT-23 package?

The MMBTA28 has a junction-to-ambient thermal resistance (R_JA) of 357 °C/W when mounted on a 36 mm × 18 mm FR-4 PCB with a minimum 6 cm² copper pad for the collector lead. This value reflects realistic SMT thermal performance and informs derating calculations - for example, at 75 °C ambient, maximum allowable power dissipation drops to approximately 265 mW. The MMBTA28 datasheet provides this figure in the Thermal Characteristics table.

MMBTA28 Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-236-3, SC-59, SOT-23-3

Packaging:: Tape & Reel (TR)

Product Status:: Active

Transistor Type:: NPN - Darlington

Current - Collector (Ic) (Max):: 800 mA

Voltage - Collector Emitter Breakdown (Max):: 80 V

Vce Saturation (Max) @ Ib, Ic:: 1.5V @ 100µA, 100mA

Current - Collector Cutoff (Max):: 500nA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 10000 @ 100mA, 5V

Power - Max:: 350 mW

Frequency - Transition:: 125MHz

Operating Temperature:: -55°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-23-3

MMBTA28 FAQ

1.How can I place an order for MMBTA28 through Aetrix?

Please submit a Request for Quotation (RFQ) for MMBTA28 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for MMBTA28 reliable?

The price and inventory of MMBTA28 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MMBTA28 is usually 5 days.

3.What payment methods are accepted for MMBTA28?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MMBTA28 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for MMBTA28?

MMBTA28 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your MMBTA28 order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for MMBTA28?

For technical support, including MMBTA28 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MMBTA28 requirements.

6.How does Aetrix verify that MMBTA28 is sourced from the original manufacturer or authorized distributors?

All MMBTA28 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that MMBTA28 meets industry standards.

7.What is the process for return or replacement of MMBTA28?

All MMBTA28 units undergo pre-shipment inspection (PSI). If there is an issue with MMBTA28, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The MMBTA28 part is unused and in its original packaging.

Return procedure for MMBTA28:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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