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BSS138

BSS138

Diodes Inc.
Discrete MOSFET commonly used in simple DIY two-line I2C level-shifter circuits.
25,546 in stock
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Overview

The BSS138 is a small-signal N-channel enhancement-mode MOSFET in a compact SOT-23 package. It is commonly used for low-voltage switching and as the transistor element in simple bidirectional two-line I2C level-shifter circuits. Its small size and low cost make it popular for hobbyist and prototyping use.

Why Choose This Part

The BSS138 is widely available, inexpensive, and packaged in a tiny SOT-23 that suits dense boards and prototyping breakouts. It is a practical choice when you need a small-signal N-channel MOSFET for level shifting or low-current switching because it supports the simple, passive MOSFET-based bidirectional level-shifter topology used in many tutorials. Its common usage means reference designs and community examples are easy to find.

Applications

I2C/SMBus bidirectional level shifting
Used as the core MOSFET in simple two-line MOSFET-based level shifters between different logic voltages.
Logic-level translation
Translating single-ended digital signals between low-voltage domains in prototype and production boards.
Low-current load switching
Switching small loads or enabling/disabling sensors and peripherals where currents are modest.
Signal gating and isolation
Temporarily isolating or gating digital lines in mixed-voltage systems.
Breadboard and prototyping
Compact SOT-23 footprint that is easy to use on breakout PCBs for quick tests and prototypes.

Getting Started

For prototyping, use a SOT-23 breakout board or socket so the BSS138 can be placed on a breadboard. When using it for two-line I2C level shifting, include pull-up resistors on both sides of the bus and follow published MOSFET level-shifter schematics found in many tutorials. If connecting to microcontrollers, you can test with Arduino or other common toolchains; treat the BSS138 as a discrete component rather than requiring any special IDE support.