BSS138

@@ -0,0 +1,47 @@+# 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++- `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)++## Provenance++Data extracted from the manufacturer datasheet, not a distributor listing:++- **Datasheet:** [Diodes Incorporated datasheet](https://www.diodes.com/assets/Datasheets/BSS138.pdf) (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](docs/bss138-nmos-datasheet.pdf)

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