BSS138T1G

Updated: 2026-09-20

Overview

The BSS138T1G is an N-channel enhancement-mode MOSFET designed for low-voltage applications. Manufactured by ON Semiconductor and other vendors, it is housed in a compact SOT-23 package, making it ideal for space-constrained designs. With a drain-source voltage (VDS) rating of 50V and continuous drain current (ID) of 220mA, it suits portable electronics and power management systems. Its low threshold voltage (typically 1.5V) ensures compatibility with logic-level signals, while its fast switching speed enhances efficiency in high-frequency circuits. The device is RoHS compliant, aligning with modern environmental standards.

Structure and Working Principle

The BSS138T1G operates as a voltage-controlled switch. When a sufficient gate-source voltage (VGS) is applied, it creates a conductive channel between the drain and source, allowing current flow. The SOT-23 package integrates three pins: gate (G), drain (D), and source (S), with a minimal footprint of 2.9mm x 1.3mm. Internally, the MOSFET leverages silicon technology to achieve low on-resistance (RDS(on) of ~3.5Ω at VGS=4.5V), reducing power loss during operation. Its enhancement-mode design ensures it remains off without gate voltage, preventing unintended conduction.

Key Features

The BSS138T1G excels in low-power applications due to its low threshold voltage (VGS(th) of 1.5V max), enabling direct drive from microcontrollers or logic circuits. Its fast switching speed (transition times in nanoseconds) minimizes delays in signal processing. Another standout feature is its low input capacitance (Ciss ≈ 50pF), which reduces gate drive requirements and improves high-frequency performance. The device also offers ESD protection (up to 2kV HBM), enhancing reliability in sensitive environments.

Application Areas

Common applications include load switching in battery-powered devices (e.g., smartphones, wearables), where its low leakage current preserves energy. It is also used in power management ICs (PMICs) for voltage regulation and in signal amplification circuits for sensors. Industrial uses encompass automation controls and low-voltage motor drivers, where its compact size and efficiency are advantageous. Additionally, it serves in audio amplifiers and LED drivers due to its fast response and minimal distortion.

Maintenance and Precautions

To ensure longevity, avoid exceeding the absolute maximum ratings (e.g., VDS=50V, ID=220mA). Static-sensitive, the device should be handled with ESD precautions, such as grounded workstations and antistatic packaging. Thermal management is critical in high-current applications; ensure adequate PCB layout for heat dissipation. For prototyping, use sockets to prevent soldering-induced damage. Store in dry, anti-static containers to mitigate moisture absorption.

B2B Procurement Guide

Bulk purchases (reels of 3,000 units) typically reduce per-unit costs by 20-30%. Verify manufacturer certifications (e.g., ON Semiconductor, Diodes Inc.) to avoid counterfeit parts. Lead times vary but average 6-8 weeks for custom orders. Key procurement considerations include RoHS compliance for global shipments and traceability documentation for quality assurance. Sample testing is recommended to validate performance in target applications before large-scale orders.