BD139 NPN Power Transistor

@@ -0,0 +1,47 @@+# BD139++**STMicroelectronics** · Bipolar Transistor (BJT) · TO-126++The BD139 is an NPN medium-power transistor rated for 80 V and 1.5 A continuous collector current in a TO-126 package. It is widely used in audio amplifier output and driver stages, discrete linear regulators, and general medium-power switching. Its complement is the BD140 PNP.++## Pinout++| Pin | Name | Type | Function |+|---|---|---|---|+| 1 | E | passive | Emitter terminal of the NPN BJT. Absolute maximum VEBO = 5 V. Typically returned to ground or a low-impedance node in common-emitter audio driver stages. |+| 2 | C | passive | Collector terminal of the NPN BJT. Absolute maximum VCEO = 80 V, VCBO = 80 V. Continuous IC = 1.5 A, peak ICM = 3 A. VCE(sat) ≤ 0.5 V at IC = 0.5 A, IB = 0.05 A. Collector tab is electrically common to the metal mounting tab of the SOT-32 package. |+| 3 | B | input | Base terminal of the NPN BJT. Absolute maximum base current IB = 0.5 A. Typical VBE ≈ 1 V at IC = 0.5 A, VCE = 2 V. Drives collector current via hFE (40-250 at IC = 150 mA). |++## Key specifications++| Parameter | Value |+|---|---|+| Type | NPN medium-power transistor |+| Collector-emitter voltage (VCEO) | 80 V |+| Collector current (IC) | 1.5 A continuous (3 A peak) |+| DC current gain (hFE) | 40 to 250 |+| Transition frequency (fT) | 190 MHz |+| Power dissipation | 12.5 W |+| Operating temperature | -55 C to 150 C |++## Ordering variants++- `BD139`+- `BD139-10`+- `BD139-16`++## CAD (KiCad official)++- Symbol: `bd139.kicad_sym`+- Footprint: `bd139.kicad_mod`+- 3D model: TO-126 body from KiCad `Package_TO_SOT_THT/TO-126-3_Vertical`.++## Provenance++Data extracted from the manufacturer datasheet, not a distributor listing:++- **Datasheet:** [STMicroelectronics datasheet](https://www.st.com/resource/en/datasheet/bd139.pdf) (9 pp, sha256 `9a72cdfa334700b8`, retrieved 2026-08-17, tier: manufacturer)+- **Extractor:** `ds2sf` (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.+- **CAD:** KiCad official libraries (CC-BY-SA 4.0).++[Datasheet PDF](docs/bd139-datasheet.pdf)

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