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BD135 NPN Power Transistor

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by Ray

NPN medium-power transistor, 45 V / 1.5 A, in TO-126 for audio and driver stages.

transistorbjtnpnmedium-powerto-126st
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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 (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