BD139 - 80V 1.5A NPN BJT TO-126 | STMicroelectronics
Teilenummer: BD139 ✓ Aktiv| Menge | Stückpreis | Gesamt |
|---|---|---|
| 1 | $0.42 | $0,42 |
| 10 | $0.36 | $3,60 |
| 100 | $0.28 | $28,00 |
| 500 | $0.22 | $110,00 |
| 1.000 | $0.18 | $180,00 |
BD139 Übersicht
A bipolar junction transistor is a current-controlled semiconductor amplifier and switch. In the power-transistor hierarchy, the BD139 sits in the medium-power class above small-signal devices such as the 2N2222 and below high-current TO-220 audio outputs. Its PNP complement is the BD140, and the pair is designed for complementary or quasi-complementary amplifier output stages.
Key features include the 80 V VCEO rating, which gives generous headroom on 24 V and 48 V rails; the 1.5 A collector current capability for driver and low-power output duties; and a DC current gain (hFE) spanning 40 to 250 across the generic grade, with ordered gain bins available as BD139-6, BD139-10, and BD139-16. According to STMicroelectronics, these epitaxial planar transistors are specifically designed for audio amplifiers and drivers utilizing complementary or quasi-complementary circuits.
Technically, the epitaxial planar construction provides stable hFE, low leakage, and a rugged 5 A peak collector current rating for reactive loads. The SOT-32 package offers a mountable tab for heatsinking, supporting the full 1.25 W rating with modest copper area, and the through-hole format simplifies hand assembly and repair.
Typical applications include class-AB audio amplifier driver and output stages, relay and solenoid drivers, LED string drivers, linear regulators, and general-purpose medium-power switching on industrial 24 V systems.
Design consideration: at high collector currents the hFE falls, so base drive must be sized for worst-case gain, and thermal design should target a junction temperature well below the 150 C maximum. Use the BD139-10 or BD139-16 gain bins when matched pairing with the BD140 complement matters.
This page synthesizes distributor pricing, verified drop-in alternatives, and practical design notes not found in the manufacturer datasheet, giving engineers a complete selection view in one place.
Drop-in-Alternativen für BD139 – gleiches Gehäuse, Pin-kompatibel. Bauteile mit anderem Gehäuse, die eine PCB-Überarbeitung erfordern, sind ausgeschlossen.
Schnellvergleichstool – Wählen Sie Alternativbauteile für den Direktvergleich:
BD139-10
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
BD139-16
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
BD139-6
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
BD139
✅ Drop-In✓ Auf Lager
$0.18 / Stück
Datenblatt ansehen →MJE242
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
BD237
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
BD139 Grenzwerte & elektrische Eigenschaften
| Transistortyp | NPN Bipolar Junction Transistor (BJT) |
| Kollektor-Emitter-Spannung (Vceo) | 80 V |
| Collector Current (IC, continuous) | 1.5 A |
| Power Dissipation (PD) | 1.25 W |
| DC Current Gain (hFE) | 40 to 250 |
| Gain Grade Options | BD139-6 / BD139-10 / BD139-16 |
| BD139-10 hFE Range | 63 to 160 |
| BD139-16 hFE Range | 100 to 250 |
| BD139-6 hFE Range | 40 to 100 |
| Complementary PNP Part | BD140 |
| Gehäuse | SOT-32 (TO-126 / TO-225AA), 3-pin through hole |
| Montageart | Through Hole |
| Technology | Epitaxial Planar Silicon |
| Configuration | Single Transistor |
| Typical Use | Audio amplifiers and drivers, complementary / quasi-complementary circuits |
BD139 Pin-Konfiguration
| Pin 1 | Emitter — Emitter of the NPN transistor; normally connected to ground or current-return path |
| Pin 2 | Collector — Collector; connects to the load or supply side of the switched/amplified circuit |
| Pin 3 | Base — Base control terminal; driven through a series resistor to set collector current |
Typische Anwendungen
BD139 ist geeignet für 6 Anwendungs: Class-AB Audio Amplifier Driver Stage, Relay and Solenoid Driver on 24 V Industrial Rails, Discrete Linear Regulator Pass Element, LED String Driver, General-Purpose Medium-Power Switching, Quasi-Complementary Output Stages in Repairs and Retro Audio.
Class-AB Audio Amplifier Driver Stage
The BD139 is purpose-built for audio amplifier driver stages: STMicroelectronics states the epitaxial planar family is designed for audio amplifiers and drivers using complementary or quasi-complementary circuits. In a typical driver role the BD139, paired with its BD140 PNP complement, drives the output transistor pairs of a class-AB amplifier, where its 80 V VCEO supports amplifier rails up to roughly +/-35 V and its 1.5 A collector current easily handles the peak drive demands of the output stage. The gain-graded BD139-10 and BD139-16 variants let designers select tighter hFE windows (63-160 and 100-250) for matched biasing and lower distortion, which matters because driver gain variation shifts the amplifier quiescent current and crossover behavior. Mounted on the amplifier heatsink via the SOT-32 tab, the device handles driver dissipation continuously. Placing a small base-stop resistor (a few ohms) prevents parasitic VHF oscillation common in driver stages.
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Relay and Solenoid Driver on 24 V Industrial Rails
The BD139 fits industrial 24 V relay and solenoid driving because its 80 V VCEO gives wide margin over the supply rail, absorbing flyback transients that survive beyond the coil-clamp diode. In this topology the collector connects to the low side of the coil, the emitter to ground, and a microcontroller or logic gate drives the base through a series resistor sized for worst-case hFE near 20-40 at the switching current, ensuring hard saturation. The 1.5 A continuous collector rating covers most PCB relays and small solenoids, and the 1.25 W dissipation in the SOT-32 tab package removes the need for a heatsink at typical coil currents. A freewheeling diode across the coil remains mandatory to keep collector voltage within rating during turn-off. Compared with a small MOSFET, the BD139 costs less and tolerates gate-less, resistor-driven logic interfaces without threshold concerns.
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Discrete Linear Regulator Pass Element
The BD139 works as a pass transistor in discrete series linear regulators, extending the output current capability of Zener-op-amp or three-terminal regulator references beyond their native limits. In this configuration the collector ties to the unregulated input (up to 80 V, well beyond standard 35 V-adjustable IC regulator ceilings) and the emitter sources regulated current to the load, with the error amplifier driving the base. The 1.5 A continuous rating and the SOT-32 tab, bolted to a chassis heatsink, allow multi-watt dissipation at moderate input-output differentials; estimated dissipation is simply (VIN - VOUT) x ILOAD, so thermal design must follow worst-case low-line/high-load conditions. The flat, predictable hFE of the epitaxial planar construction keeps loop gain stable, and the through-hole package simplifies service in laboratory and repair power supplies where the BD139 has been a workhorse for decades.
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LED String Driver
The BD139 is a cost-effective linear current regulator for LED strings on 24 V and 48 V supplies. Operating in its active region as a controlled current source, the BD139 sets string current with an emitter resistor and a base voltage derived from a reference, providing ripple-free, flicker-free LED drive without switching EMI - valuable in architectural and display lighting. Its 80 V VCEO allows long LED strings on a 48 V rail with ample breakdown margin, while the 1.5 A continuous rating covers strings of several high-brightness LEDs. Dissipation equals (VSUPPLY - VSTRING) x ILED, so the SOT-32 tab should couple to a metal chassis or PCB copper pour for strings dissipating more than roughly 0.5 W; this is a deliberate trade-off of efficiency for EMI silence compared with switch-mode LED drivers. Gain-bin variants such as BD139-10 make current setting more repeatable across production units.
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General-Purpose Medium-Power Switching
As a general-purpose medium-power NPN switch, the BD139 covers loads from a few hundred milliamps up to 1.5 A at up to 80 V - a niche small-signal transistors (limited near 40 V and under 1 A) and MOSFETs (requiring gate drivers above logic levels) both miss. Typical uses include motor enable switches, buzzer and lamp drivers, bias generators, and protection crowbars on 24 V industrial boards. Driven into saturation with a base current near one-twentieth of the collector current, the device exhibits a low collector-emitter saturation voltage, keeping on-state dissipation modest; the through-hole SOT-32 package also tolerates hand soldering, making it a repair-shop staple. The trade-off versus a MOSFET is continuous base current consumption, which matters only in battery-powered designs. For pulse loads, verify against the SOA data in the manufacturer datasheet rather than extrapolating from the DC rating.
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Quasi-Complementary Output Stages in Repairs and Retro Audio
In quasi-complementary amplifier output stages - common in vintage and budget audio designs - a BD139 driver works with a BD140 and a pair of same-polarity output devices to synthesize push-pull operation. The BD139 is a frequent replacement in amplifier repair because its 80 V / 1.5 A ratings and SOT-32 footprint match the original driver positions of countless classic amplifiers, and current production from STMicroelectronics and onsemi keeps it available. When restoring such equipment, selecting gain-binned parts (BD139-10 with BD140-10) restores the original symmetric-gain intent, reducing quiescent-current drift and crossover distortion. Repair practice recommends replacing driver pairs together, verifying bias with a multimeter across emitter resistors, and applying thermal compound under the tab. Community forums such as DIYaudio regularly confirm BD139/BD140 availability and substitution guidance for out-of-stock legacy drivers.
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Zusammenfassung der empfohlenen Produkte
Technische Referenzdaten für BD139 – Vergleich, Designhinweise und Compliance-Informationen.
Auswahlhilfe
Vergleich mit Alternativen
| Parameter | Dieses Produkt | BD139-10 | BD139-16 | BD139 (onsemi) | MJE242 | BD237 |
|---|---|---|---|---|---|---|
| Package | SOT-32 (TO-126), 3-pin through hole | SOT-32 (TO-126) - same | SOT-32 (TO-126) - same | TO-225AA (TO-126-compatible) - same footprint | TO-126 - same | SOT-32 (TO-126) - same |
| Brand | STMicroelectronics | STMicroelectronics | STMicroelectronics | onsemi | onsemi | STMicroelectronics |
| Polarity | NPN | NPN | NPN | NPN | NPN | NPN |
| Drop-in Compatibility | Reference device | Pin-to-pin, identical die | Pin-to-pin, identical die | Pin-to-pin, footprint-compatible | Pin-to-pin, verify parameters | Pin-to-pin, verify parameters |
Wichtigste Unterscheidungsmerkmale
- Purpose-designed for complementary audio driver circuits (vs. MJE242)
- Factory gain binning available in the same footprint (vs. BD139-10)
- 80 V VCEO exceeds same-class small-signal devices (vs. BD237)
Designhinweise
Size base drive for worst-case gain, not typical. hFE for the generic BD139 spans 40-250 and drops at high collector current and low temperature, so design the base current for an effective forced gain of 20-40 when saturating the device. Under-driven BD139s run hot in switching duty and may fail the load regulation spec. If matching matters (audio drivers), order BD139-10 or BD139-16 gain bins instead of sorting generic units.
Estimated: the 1.25 W rating assumes the SOT-32 tab is effectively coupled to a heatsink or large copper area. For free-air mounting, derate substantially - a rule of thumb is roughly 0.6-0.8 W usable. Compute dissipation as VCE x IC (switching) or (VIN - VOUT) x ILOAD (linear use) and keep the estimated junction below about 100 C for long-term reliability. Apply thermal compound and torque the tab fastener properly in amplifier repairs.
In audio driver and high-current linear roles, add a small base-stop resistor (2.2-10 ohm) close to the base pin to damp parasitic oscillation, which epitaxial planar power BJTs can exhibit at VHF with long or inductive leads. Keep the base trace short, and place the emitter connection at a single low-impedance ground point to prevent common-impedance coupling between driver and output stages.
Always fit a flyback diode across inductive loads (relays, solenoids, small motors). Even with a clamp diode, wiring inductance can transiently raise the collector above the 80 V VCEO, so keep the loop from BD139 collector to load to diode short. For higher-energy inductive loads, verify the actual stress against the SOA curve in the manufacturer datasheet rather than relying on the DC ratings alone.
Compliance-Informationen
RoHS/REACH/lead-free status is assigned per orderable suffix (e.g. -BP packaging codes) and was not stated in the provided verified web data; confirm on the distributor product page for the exact ordering code.
