onsemi BD139

Overview

BD139 from onsemi is a plastic medium-power silicon NPN transistor designed for audio amplifier and driver stages in complementary or quasi-complementary circuits, with V_CEO = 80 V, I_C = 1.5 A, P_D = 12.5 W at T_C = 25°C, h_FE ≥ 25 (at I_C = 0.5 A), and TO-225 package. It operates across –55°C to +150°C junction temperature.

For engineers reviewing the BD139 datasheet, pinout, applications, or equivalent options, key selection considerations include its 80 V V_CEO rating, 12.5 W case-rated power dissipation, DC current gain range (25–250), saturation voltage (≤0.5 V at I_C = 0.5 A, I_B = 0.05 A), and thermal resistance (R_JC = 10°C/W).

Technical Context

The BD139 functions as a linear or switching NPN bipolar junction transistor in medium-power analog and power amplification stages. Its design supports operation with base-emitter on voltage ≤1.0 V and collector-emitter saturation voltage ≤0.5 V under specified drive conditions, enabling efficient current control in Class AB audio output stages.

It is explicitly complementary to the BD140 PNP transistor and shares identical TO-225 mechanical outline and thermal characteristics with BD135G and BD137G - differing only in breakdown voltage ratings (V_CEO, V_CBO) and corresponding safe operating area boundaries.

Key Specifications

Pinout & Package

BD139 is housed in a TO-225 package (Case 77-09, Style 1) with three leads and an electrically connected metal tab (pins 2 and 4 both connect to collector). The package provides mechanical robustness and thermal path via the collector-connected tab.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BD139-16 and MJE13009, the BD139 offers balanced voltage/current capability and gain range in a cost-effective TO-225 package ideal for audio and general-purpose medium-power linear/switching roles - whereas BD139-16 trades broader gain tolerance for tighter binning, and MJE13009 shifts focus to high-voltage switching at the expense of gain and package compatibility.

Availability

BD139 is available at Aetrix Electronics and suitable for audio amplifier output stages, DC motor drivers, linear regulator pass elements, and relay/LED interface circuits requiring stable component supply and long-term industrial availability.

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

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

The BD139 belongs to onsemi's legacy medium-power bipolar transistor product line, engineered specifically for cost-sensitive, thermally demanding linear and switching applications in audio, power supply, and electromechanical control systems.

FAQ

What is the maximum collector-emitter voltage rating for BD139?

The BD139 has a maximum collector-emitter sustaining voltage (V_CEO) of 80 Vdc, tested at I_C = 30 mA and I_B = 0. This rating defines the absolute upper limit for voltage applied between collector and emitter while maintaining safe operation without avalanche breakdown. Exceeding this value risks irreversible device failure, especially under transient conditions.

Does BD139 have a built-in heatsink interface?

Yes - the BD139 uses a TO-225 package where pins 2 and 4 are internally connected to the collector and also to the metal tab on the backside. This tab serves as a direct thermal interface to an external heatsink, enabling efficient heat removal. Thermal resistance from junction to case (R_JC) is specified at 10°C/W, confirming its suitability for heatsink-mounted operation at up to 12.5 W dissipation.

Is BD139 RoHS-compliant and lead-free?

Yes, the BD139G variant is explicitly designated as Pb-free, halogen-free/BFR-free, and RoHS-compliant per onsemi documentation. The "G" suffix in the part number (BD139G) indicates conformance to EU RoHS Directive 2011/65/EU and related environmental standards. This applies to both material composition and manufacturing process.

Can BD139 be used as a direct replacement for BD135G or BD137G?

No - while BD139 shares the same TO-225 package, pinout, and thermal specifications with BD135G and BD137G, it is not a direct replacement due to higher voltage ratings: BD139 has V_CEO = 80 V and V_CBO = 100 V versus 45 V and 45 V for BD135G, and 60 V and 60 V for BD137G. Substituting BD139 in circuits designed for lower-voltage variants may cause overdesign or unintended stress on supporting components.

What is the typical DC current gain (h_FE) range for BD139 at 0.5 A collector current?

At I_C = 0.5 A and V_CE = 2 V, the BD139 exhibits a DC current gain (h_FE) ranging from 25 (minimum) to 250 (maximum), per onsemi's Electrical Characteristics table. This wide spread reflects process variation and must be accounted for in base drive design - e.g., using worst-case h_FE = 25 to ensure saturation under all conditions.