BD135 NPN Power Transistor

@@ -0,0 +1,46 @@+# BD135++**STMicroelectronics** · Bipolar Transistor (BJT) · TO-126++The BD135 is an NPN medium-power transistor rated for 45 V and 1.5 A continuous collector current in a TO-126 package. It is the lower-voltage member of the BD135/137/139 NPN series, used in audio driver and output stages, discrete regulators, and medium-power switching.++## Pinout++| Pin | Name | Type | Function |+|---|---|---|---|+| 1 | E | passive | Emitter. Common-emitter reference for the NPN device. VEBO max = 5 V; typically tied to the low-side rail or output node depending on topology. |+| 2 | C | passive | Collector. Electrically connected to the metal mounting tab. VCBO max = 45 V, VCEO max = 45 V, IC max = 1.5 A continuous (3 A peak). Thermal path to case: Rthj-case = 10 °C/W. |+| 3 | B | input | Base. Controls collector current via base-emitter forward bias. VBE(on) ≈ 1 V at IC = 0.5 A; VEBO absolute max = 5 V; IB max = 0.5 A. |++## Key specifications++| Parameter | Value |+|---|---|+| Type | NPN medium-power transistor |+| Collector-emitter voltage (VCEO) | 45 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++- `BD135`+- `BD135-16`++## CAD (KiCad official)++- Symbol: `bd135.kicad_sym`+- Footprint: `bd135.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/bd135.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/bd135-datasheet.pdf)

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