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

STMicroelectronics BD139

Name: BD139
Brand: STMicroelectronics
SKU: BD139
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BD139

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-225AA, TO-126-3

Datasheet:: BD139.pdf

Description:: TRANS NPN 80V 1.5A SOT-32-3

Quantity:: RFQ Add To RFQ list

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Inventory:6,345

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Product details

Overview

BD139 from STMicroelectronics is an NPN epitaxial planar bipolar junction transistor in SOT-32 package, rated for 80 V V_CEO, 1.5 A continuous collector current, and 12.5 W case dissipation at T_C ≤ 25 °C. It serves as a medium-power audio driver in complementary quasi-complementary amplifier stages.

For engineers reviewing the BD139 datasheet, BD139 pinout, BD139 application, or BD139 equivalent, key selection criteria include DC current gain grouping (BD139-10: h_FE = 63–100; BD139-16: h_FE = 160–250), safe operating area under pulsed conditions, and thermal resistance (R_thj-case = 10 °C/W).

Technical Context

The BD139 operates as a linear amplifying device with fixed-base biasing capability, supporting Class AB push-pull output stages. Its h_FE is specified across three test points (IC = 5 mA, 150 mA, 0.5 A), enabling predictable gain behavior in both small-signal pre-driver and medium-current output roles.

It features low V_CE(sat) of 0.5 V at IC = 0.5 A / IB = 0.05 A and V_BE ≈ 1 V under same conditions, ensuring efficient switching and minimal base drive loss in quasi-complementary configurations.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	80 V - supports rail voltages up to ±40 V in split-supply audio amplifiers
I_C (continuous)	1.5 A - drives 4–8 Ω speaker loads with peak power handling >10 W
P_TOT (T_C ≤ 25 °C)	12.5 W - requires heatsinking when operated above ~2 W ambient dissipation
h_FE (IC = 150 mA)	63–250 - pre-selected gain groups enable matched pair assembly for low-distortion output stages
V_CE(sat)	0.5 V @ IC = 0.5 A - reduces conduction loss and thermal stress in linear output operation
R_thj-case	10 °C/W - enables direct mounting to aluminum heatsink without thermal interface pad for moderate duty cycles

Pinout & Package

SOT-32 (TO-126) plastic package with vertical mounting orientation, metal tab connected to collector for thermal conduction and electrical grounding in PCB layout.

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	Current sink terminal	Connected to ground or negative rail in common-emitter amplifier configuration
2 (Base)	Control input	Receives current-limited drive signal; requires series resistor to limit IB ≤ 0.5 A
3 (Collector / Tab)	Main current path & thermal interface	Electrically and thermally tied to heatsink; must be isolated from other potentials unless grounded

Key Features

Feature	Design Value
Pre-selected h_FE groups	BD139-10 (63–100) and BD139-16 (160–250) allow precise matching for push-pull symmetry
High V_CEO rating	80 V enables use in higher-voltage audio supplies (e.g., ±35 V rails) without derating
Low saturation voltage	V_CE(sat) = 0.5 V minimizes power loss and self-heating during high-current conduction
ECOPACK® compliance	Lead-free second-level interconnect meets JEDEC JESD97; RoHS-compliant soldering profile

Applications

Hi-Fi Audio Power Amplifier

DC Motor Driver Stage

Use Scenario: Medium-power stereo amplifier output stage delivering 10–15 W into 8 Ω load.

IC Role / Device Role / Timing Role: NPN complement in quasi-complementary emitter-follower output pair.

Use Value: Matched h_FE groups reduce crossover distortion; 80 V V_CEO accommodates ±35 V supply rails.

Use Scenario: H-bridge half-bridge driver controlling 12 V/1 A brushed DC motor.

IC Role / Device Role / Timing Role: High-side NPN switch in discrete totem-pole driver feeding MOSFET gate.

Use Value: 1.5 A I_C and 0.5 V V_CE(sat) ensure fast, low-loss turn-on of power FETs.

Intercom Audio Output

LED Array Current Regulator

Use Scenario: Public address intercom station with 5 W speaker output and battery backup.

IC Role / Device Role / Timing Role: Single-ended Class A/B driver stage with emitter degeneration resistor.

Use Value: Stable h_FE over temperature ensures consistent gain across 0–50 °C operating range.

Use Scenario: Constant-current driver for 24 V, 350 mA LED string in industrial signage.

IC Role / Device Role / Timing Role: Linear current-pass element controlled by op-amp feedback loop.

Use Value: 12.5 W P_TOT allows 350 mA × 24 V = 8.4 W dissipation with adequate heatsink margin.

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN medium-power BJT applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
BD239	V_CEO = 100 V, I_C = 2 A, h_FE min = 40 (unbinned)	Higher voltage headroom but no factory h_FE binning; wider gain scatter	Select when V_CEO > 80 V is required and gain matching is secondary
MJE13003	V_CEO = 400 V, I_C = 1.5 A, slower switching (f_T ≈ 4 MHz)	Designed for SMPS flyback switches; unsuitable for linear audio due to poor linearity	Avoid in audio or linear regulator roles; only consider for high-voltage switching where gain stability is not critical

Compared with BD239 and MJE13003, the BD139 offers factory-binned h_FE and optimized linearity for analog amplification-making it preferred for low-distortion audio output stages despite lower V_CEO than BD239 and narrower application scope than MJE13003.

Availability

BD139 is available at Aetrix Electronics and suitable for Hi-Fi audio amplifiers, DC motor drivers, intercom systems, and LED current regulators requiring stable component supply and long-term manufacturability.

Supply support for BD139 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The BD139 belongs to ST's legacy bipolar power transistor family, engineered specifically for cost-sensitive, medium-power linear amplification and driver applications where gain consistency and thermal reliability are prioritized over RF or switching speed.

FAQ

Is BD139 pin-compatible with BD135?

Yes, BD139 and BD135 share identical SOT-32 pinout (E-B-C) and mechanical footprint. However, BD139 has higher V_CEO (80 V vs. 45 V) and higher h_FE minimum (25 vs. 25, but binned variants differ), making it a direct upgrade in voltage-critical designs-but not a guaranteed drop-in replacement without verifying SOA margins.

What is the maximum safe continuous collector current at 70 °C case temperature?

At T_C = 70 °C, derating per Figure 3 reduces P_TOT to ≈ 5 W. With V_CE(sat) ≈ 0.5 V, maximum continuous I_C is limited to √(P_TOT/R_CE(sat)) ≈ 3.16 A theoretically-but absolute max I_C remains 1.5 A per Table 2. So 1.5 A is the hard limit regardless of temperature.

Can BD139 be used in switching power supplies?

BD139 is not optimized for switching applications: its f_T is unlisted in the datasheet, storage time (t_s) is unspecified, and SOA curves emphasize linear operation. While usable in low-frequency (<10 kHz) flyback or relay drivers, dedicated switching transistors like BUJ302A offer superior speed, SOA, and safe switching margins.

Does BD139 require a heatsink in typical audio amplifier use?

Yes-when dissipating >2 W continuously (e.g., 0.5 A × 4 V = 2 W), thermal resistance R_thj-amb = 100 °C/W would raise junction temperature beyond safe limits. A 20 °C/W heatsink plus thermal pad reduces total R_th to ~30 °C/W, keeping T_j < 100 °C at 2 W ambient dissipation.

BD139 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-225AA, TO-126-3

Packaging:: Tube

Product Status:: Active

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 1.5 A

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

Vce Saturation (Max) @ Ib, Ic:: 500mV @ 50mA, 500mA

Current - Collector Cutoff (Max):: 100nA (ICBO)

DC Current Gain (hFE) (Min) @ Ic, Vce:: 40 @ 150mA, 2V

Power - Max:: 1.25 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: SOT-32-3

BD139 FAQ

1.How can I place an order for BD139 through Aetrix?

Please submit a Request for Quotation (RFQ) for BD139 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 BD139 reliable?

The price and inventory of BD139 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BD139 is usually 5 days.

3.What payment methods are accepted for BD139?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BD139 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BD139?

BD139 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BD139 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 BD139?

For technical support, including BD139 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BD139 requirements.

6.How does Aetrix verify that BD139 is sourced from the original manufacturer or authorized distributors?

All BD139 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 BD139 meets industry standards.

7.What is the process for return or replacement of BD139?

All BD139 units undergo pre-shipment inspection (PSI). If there is an issue with BD139, 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 BD139 part is unused and in its original packaging.

Return procedure for BD139:

1.Submit a request within 90 days.

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

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