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

onsemi MMBT6428

Name: MMBT6428
Brand: onsemi
SKU: MMBT6428
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: MMBT6428

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: MMBT6428.pdf

Description:: TRANS NPN 50V 0.5A SOT-23-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

MMBT6428 from Fairchild Semiconductor is an NPN general-purpose amplifier transistor in SOT-23 package, rated for 50 V V_CEO, 500 mA continuous I_C, and 100–700 MHz f_T, used in low-power signal amplification stages of consumer audio and sensor interface circuits.

For engineers reviewing the MMBT6428 datasheet, pinout, applications, or equivalent options, key selection considerations include its 250–650 h_FE range at 10 µA–10 mA I_C, 0.2 V V_CE(sat) at 10 mA/0.5 mA drive, and thermal resistance of 357 °C/W on FR-4 PCB.

Technical Context

The MMBT6428 operates as a silicon NPN bipolar junction transistor optimized for linear amplification up to 300 mA collector current, with guaranteed h_FE ≥250 across four decades of I_C (10 µA to 10 mA) at V_CE = 5 V. Its f_T spans 100–700 MHz under standard bias, supporting RF front-end and broadband preamplifier use.

Thermal design relies on its 350 mW P_D at 25°C with 2.8 mW/°C derating, and R_θJA = 357 °C/W on a 1.6" × 1.6" FR-4 board - critical for compact PCB layouts where ambient temperature rise must be constrained below 125°C.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	50 V - maximum safe voltage between collector and emitter before breakdown; defines usable supply headroom in common-emitter amplifier stages.
I_C (continuous)	500 mA - absolute max DC collector current; practical linear operation limited to ≤300 mA per device description.
h_FE	250–650 - DC current gain range at V_CE = 5 V; enables predictable biasing across production lots for stable small-signal gain.
f_T	100–700 MHz - unity-gain bandwidth; supports amplification up to ~100 MHz with usable gain margin in RF applications.
V_CE(sat)	0.2 V @ 10 mA/0.5 mA - low saturation voltage ensures minimal power loss and voltage drop in switching or Class-A amplifier output stages.
R_θJA	357 °C/W - junction-to-ambient thermal resistance on standard FR-4; dictates required board copper area and airflow for thermal compliance.

Pinout & Package

SOT-23 plastic surface-mount package (3-pin, 1.90 mm × 1.30 mm footprint), marked "1K", with lead-free finish compliant to RoHS Directive 2002/95/EC.

Pin/Terminal	Circuit Role	Design Meaning
1 (Base)	Current-controlled input terminal	Accepts base drive current to modulate collector current; requires external bias network for stable Q-point setting.
2 (Emitter)	Common reference terminal	Typically tied to ground or local return; carries full emitter current (I_E ≈ I_C + I_B) and sets DC path for bias stability.
3 (Collector)	Output current terminal	Delivers amplified load current; connected to supply rail via collector resistor or active load in common-emitter configuration.

Key Features

Feature	Design Value
High DC current gain consistency	h_FE ≥250 at I_C = 10 µA–10 mA ensures reliable bias point establishment without trimming in production designs.
Low V_CE(sat) at moderate drive	0.2 V at I_C/I_B = 10 mA/0.5 mA reduces conduction loss and improves efficiency in Class-A amplifiers.
Wide f_T range	100–700 MHz supports broadband small-signal amplification up to VHF band without external neutralization.
Controlled leakage performance	ICEO ≤ 0.1 µA at V_CE = 30 V minimizes standby current in battery-powered sensor front-ends.

Applications

Audio Pre-amplifier Stage	Temperature Sensor Interface
Use Scenario: Low-noise voltage amplification of electret microphone output prior to ADC sampling in portable voice recorders. IC Role / Device Role / Timing Role: NPN small-signal amplifier configured in common-emitter topology with emitter degeneration for gain stability. Use Value: 250–650 h_FE and 0.2 V V_CE(sat) enable high input impedance and low distortion at 1–5 V supply rails.	Use Scenario: Linear amplification of millivolt-level output from silicon diode-based temperature sensors in HVAC control modules. IC Role / Device Role / Timing Role: Transconductance amplifier stage converting sensor voltage to buffered current for ratiometric ADC reference scaling. Use Value: Tight ICEO ≤ 0.1 µA ensures negligible offset drift over -55°C to 125°C operating range.
RF Signal Booster	LED Driver Bias Control
Use Scenario: Wideband gain block in 2.4 GHz ISM-band receiver LNA input matching network for IoT wireless nodes. IC Role / Device Role / Timing Role: Small-signal NPN amplifier operating in common-base configuration for improved high-frequency stability. Use Value: f_T up to 700 MHz provides >15 dB gain margin at 250 MHz, enabling single-stage amplification without peaking networks.	Use Scenario: Constant-current source control element in analog dimming circuit for indicator LEDs on industrial HMI panels. IC Role / Device Role / Timing Role: Linear-mode current regulator using emitter-follower configuration with precision base voltage reference. Use Value: 500 mA I_C rating and 350 mW P_D support 20–100 mA LED loads with <1% current variation over temperature.

Audio Pre-amplifier Stage

Temperature Sensor Interface

Use Scenario: Low-noise voltage amplification of electret microphone output prior to ADC sampling in portable voice recorders.

IC Role / Device Role / Timing Role: NPN small-signal amplifier configured in common-emitter topology with emitter degeneration for gain stability.

Use Value: 250–650 h_FE and 0.2 V V_CE(sat) enable high input impedance and low distortion at 1–5 V supply rails.

Use Scenario: Linear amplification of millivolt-level output from silicon diode-based temperature sensors in HVAC control modules.

IC Role / Device Role / Timing Role: Transconductance amplifier stage converting sensor voltage to buffered current for ratiometric ADC reference scaling.

Use Value: Tight ICEO ≤ 0.1 µA ensures negligible offset drift over -55°C to 125°C operating range.

RF Signal Booster

LED Driver Bias Control

Use Scenario: Wideband gain block in 2.4 GHz ISM-band receiver LNA input matching network for IoT wireless nodes.

IC Role / Device Role / Timing Role: Small-signal NPN amplifier operating in common-base configuration for improved high-frequency stability.

Use Value: f_T up to 700 MHz provides >15 dB gain margin at 250 MHz, enabling single-stage amplification without peaking networks.

Use Scenario: Constant-current source control element in analog dimming circuit for indicator LEDs on industrial HMI panels.

IC Role / Device Role / Timing Role: Linear-mode current regulator using emitter-follower configuration with precision base voltage reference.

Use Value: 500 mA I_C rating and 350 mW P_D support 20–100 mA LED loads with <1% current variation over temperature.

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN general-purpose amplifier applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
BC846B	Lower V_CEO (65 V), higher h_FE min (200–450), same SOT-23 package	Optimized for higher-voltage switching; less suitable for low-V_CE linear amplification due to higher V_CE(sat)	Select when higher breakdown voltage is required and gain linearity at sub-1 mA I_C is not critical.
MPSA18	TO-92 package, higher P_D (1 W), lower f_T (150 MHz), V_CEO = 50 V	Through-hole mounting only; suited for prototyping or high-power discrete stages where thermal mass matters more than size.	Choose for manual assembly, legacy board compatibility, or when >350 mW dissipation is needed with forced-air cooling.

Compared with BC846B and MPSA18, the MMBT6428 delivers superior f_T and lower V_CE(sat) in SOT-23, making it preferred for space-constrained, high-frequency linear amplification where thermal resistance ≤357 °C/W is acceptable.

Availability

MMBT6428 is available at Aetrix Electronics and suitable for audio pre-amplifier stages, temperature sensor interfaces, RF signal boosters, and LED driver bias control requiring stable component supply and consistent h_FE performance across production batches.

Supply support for MMBT6428 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power management, analog, and discrete components before its acquisition by ON Semiconductor in 2016.

The MMBT6428 belongs to Fairchild's general-purpose bipolar transistor product line, designed specifically for cost-sensitive, medium-frequency linear amplification in consumer and industrial electronics.

FAQ

What is the maximum continuous collector current rating for the MMBT6428?

The MMBT6428 has a maximum continuous collector current (I_C) rating of 500 mA at T_C = 25°C. However, the device datasheet explicitly states it is designed for general-purpose amplifier applications "at collector currents to 300 mA", indicating that 300 mA represents the recommended upper limit for reliable linear operation under typical thermal conditions. Derating applies above 25°C per the 2.8 mW/°C specification.

Does the MMBT6428 support RF amplification up to 500 MHz?

Yes, the MMBT6428 supports RF amplification up to 500 MHz in practical designs. Its f_T is specified from 100 MHz to 700 MHz at V_CE = 5 V, I_C = 1 mA, and f = 100 MHz. At 500 MHz, usable gain is achievable in common-emitter or common-base configurations with proper impedance matching - confirmed by its 3.0 pF C_obo and 8.0 pF C_ibo enabling stable broadband tuning.

What is the pin configuration of the MMBT6428 in SOT-23 package?

The MMBT6428 uses standard SOT-23 pinout: Pin 1 is Base, Pin 2 is Emitter, and Pin 3 is Collector. This matches JEDEC TO-236AB outline and is verified by Fairchild's official package drawing and marking "1K" orientation. The device is not pin-compatible with SOT-23 PNP variants or MOSFETs sharing the same footprint.

How does the MMBT6428's thermal resistance affect PCB layout?

The MMBT6428 has R_θJA = 357 °C/W on a 1.6" × 1.6" FR-4 board. To maintain T_J ≤ 150°C at full 350 mW dissipation, ambient temperature must stay below 55°C - requiring either reduced power operation, added copper pour under the pad, or localized airflow. Layouts omitting thermal relief or using 0.8 mm² pads will exceed this rating significantly.

Is the MMBT6428 suitable for use in automotive temperature sensing circuits?

Yes, the MMBT6428 is suitable for automotive temperature sensing circuits within its qualified operating range. Its T_J rating of –55°C to +150°C meets AEC-Q101 stress test thresholds for discrete transistors, and its ICEO ≤ 0.1 µA at 30 V ensures minimal drift in sensor amplifier offset over the full automotive ambient range. It is not AEC-Q101 certified out-of-box but is widely used in non-safety-critical cabin sensor nodes.

MMBT6428 Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

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

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 500 mA

Voltage - Collector Emitter Breakdown (Max):: 50 V

Vce Saturation (Max) @ Ib, Ic:: 600mV @ 5mA, 100mA

Current - Collector Cutoff (Max):: 100nA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 250 @ 100µA, 5V

Power - Max:: 350 mW

Frequency - Transition:: 700MHz

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

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-23-3

MMBT6428 FAQ

1.How can I place an order for MMBT6428 through Aetrix?

Please submit a Request for Quotation (RFQ) for MMBT6428 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 MMBT6428 reliable?

The price and inventory of MMBT6428 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MMBT6428 is usually 5 days.

3.What payment methods are accepted for MMBT6428?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MMBT6428 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for MMBT6428?

MMBT6428 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your MMBT6428 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 MMBT6428?

For technical support, including MMBT6428 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MMBT6428 requirements.

6.How does Aetrix verify that MMBT6428 is sourced from the original manufacturer or authorized distributors?

All MMBT6428 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 MMBT6428 meets industry standards.

7.What is the process for return or replacement of MMBT6428?

All MMBT6428 units undergo pre-shipment inspection (PSI). If there is an issue with MMBT6428, 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 MMBT6428 part is unused and in its original packaging.

Return procedure for MMBT6428:

1.Submit a request within 90 days.

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

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