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BSS138LT1G

ONBSS138LT1G

onsemi
N-Channel 50 V 200mA (Ta) 225mW (Ta) Surface Mount SOT-23-3 (TO-236)
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Overview

The BSS138LT1G is a logic-level N-Channel MOSFET designed for low-voltage, low-power switching applications. It features a very low gate threshold voltage of 0.5V to 1.5V, making it ideal for interfacing directly with low-voltage microcontrollers and digital logic. Housed in a standard SOT-23 package, it is a staple component for level shifting and small signal control.

Why Choose This Part

The primary advantage is the exceptionally low Vgs(th), which allows the FET to fully saturate even with 1.8V logic levels. It offers a high drain-source breakdown voltage of 50V in a compact SOT-23 footprint, providing a robust safety margin for 12V and 24V bus applications. Additionally, the device supports a wide operating junction temperature range from -55C to 150C.

Applications

Logic Level Shifting
Translating signals between low-voltage logic (e.g., 1.8V or 2.5V) and higher voltage rails up to 50V.
Load Switching
Controlling small peripheral loads such as LEDs, buzzers, or small relays with a continuous drain current up to 200mA.
DC-DC Converters
Acting as a switching element in low-power boost or buck converters for portable electronics.
Power Management
Implementing power-path control and battery protection circuits in compact, battery-operated devices.

Key Specifications

FET Type N-Channel
Vgs (Max) +/-20V
Technology MOSFET (Metal Oxide)
Mounting Type Surface Mount
Package / Case TO-236-3, SC-59, SOT-23-3
Vgs(th) (Max) @ Id 1.5V @ 1mA
Operating Temperature -55degC ~ 150degC (TJ)
Rds On (Max) @ Id, Vgs 3.5Ohm @ 200mA, 5V
Power Dissipation (Max) 225mW (Ta)
Supplier Device Package SOT-23-3 (TO-236)
Drain to Source Voltage (Vdss) 50 V
Input Capacitance (Ciss) (Max) @ Vds 50 pF @ 25 V
Drive Voltage (Max Rds On, Min Rds On) 5V
Current - Continuous Drain (Id) @ 25degC 200mA (Ta)

Getting Started

When designing with the BSS138, ensure the gate-to-source voltage stays within the +/-20V limit and account for the 3.5 Ohm Rds(on) when calculating thermal dissipation at the 200mA maximum current. For breadboard prototyping, use a SOT-23 to DIP adapter board since this is a surface-mount component. Most modern PCB EDA tools like KiCad or Altium include this standard footprint in their default libraries.