SOT23

SOT-23, short for Small Outline Transistor, is a widely used three-terminal surface-mount package for semiconductors. While named for transistors, the package is also used for diodes, voltage regulators, and other three-terminal devices. The SOT-23-3 variant is the standard form factor and is common across many manufacturers.

The package is a small rectangular body, typically about 3.0 mm long and 1.3 mm wide, with three gull-wing leads. Two leads extend from one side and a single lead comes from the opposite side. Pin 1 is usually indicated by a notch or bevel on the top surface to aid correct orientation during PCB assembly.

SOT-23 devices cover a broad range of functions, including NPN and PNP bipolars, various types of MOSFETs, diodes, and low-power linear regulators. Their compact size makes them well-suited for portable and space-constrained electronics, where low to modest power dissipation is acceptable.

In manufacturing, SOT-23 parts are designed for surface-mount technology. They are typically mounted on a PCB using reflow soldering with a three-pad footprint that matches the three leads. Precise alignment and paste deposition are important to avoid solder bridging and misorientation.

Limitations of SOT-23 devices include restricted current handling and heat dissipation due to small size. They are intended for low-power applications and are often used with thermal management considerations when higher power is required.