component

BSS138

Public Made by Adom

by adom

Diodes Inc N-channel logic-level MOSFET, SOT-23. 50 V, low Vgs(th), the I2C level-shift MOSFET. Datasheet-verified.

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Made with kicad-footprint-generator 10.0 · KiCad file format 20260206
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docs bss138-nmos: re-etch, flat white mark read from pin 1 (service-occt 1.4.0) + chip hero · Ray 1mo ago
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bss138-nmos-etched.step bss138-nmos: re-etch, flat white mark read from pin 1 (service-occt 1.4.0) + chip hero · Ray 1mo ago
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BSS138

Diodes Incorporated · N-channel logic-level MOSFET · SOT-23

A small N-channel logic-level MOSFET in SOT-23, most famous as the switch in bidirectional I2C and logic level shifters. Its gate threshold is low enough (around 1.5 V) to turn fully on from 3.3 V or even lower logic, and it handles up to 50 V drain-source and a couple hundred milliamps, so it also drives small loads, LEDs, and gate signals. In the classic level-shifter circuit one BSS138 per line, with pull-ups to each rail, passes signals both ways between a 3.3 V and a 5 V bus. Pinout is G, S, D.

Pinout

Pin Name Type Function
1 G input Gate. Controls the MOSFET channel. VGS(TH) typ 1.2 V (0.5 V min, 1.5 V max). Continuous VGSS = ±20 V max. Input capacitance Ciss ≤ 50 pF @ VDS = 10 V.
2 S passive Source. Reference terminal for VGS; connects to the internal body-diode anode. Continuous drain current ID = 200 mA (IDM pulsed = 1 A).
3 D passive Drain. Switched terminal; internal body-diode cathode. BVDSS = 50 V min, RDS(ON) typ 1.4 Ω (3.5 Ω max) @ VGS = 10 V, ID = 0.22 A.

Key specifications

Parameter Value
Type N-channel MOSFET (logic-level)
Drain-source (VDS) 50 V
Gate threshold (Vgs(th)) 0.8-1.5 V
Continuous drain current ~200 mA
RDS(on) ~3.5 Ω at VGS=10 V
Common use I2C / logic level shifting
Pinout G-S-D
Package SOT-23

Ordering variants

Same part, different packaging or reel option.

  • BSS138-7-F (SOT-23)
  • BSS138W-7-F (SOT-323)

CAD (KiCad official)

  • Symbol: Transistor_FET:BSS138
  • Footprint: Package_TO_SOT_SMD:SOT-23
  • 3D model: SOT-23 (KiCad packages3D)
  • 3D model files: bss138-nmos-etched.step / bss138-nmos-etched.glb carry the MPN laser-etched on the die in a toggleable Adom.LaserEtch group (Fusion-ready); bss138-nmos.step / bss138-nmos.glb are the bare package body.

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

  • Datasheet: Diodes Incorporated datasheet (6 pp, sha256 c93dcb33f41424e6, 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