BSS138LT1 N-Channel Power MOSFET 200mA 50V SOT−23

BSS138LT1 N-Channel Power MOSFET (200mA, 50V, SOT-23) is a small-signal, enhancement-mode field-effect transistor specifically engineered for low-power switching applications in miniature electronic designs. This high-efficiency N-Channel MOSFET provides an excellent solution for driving loads that require continuous drain currents up to 200 mA and can easily handle voltages up to 50 V. Consequently, designers frequently select the BSS138LT1 for interfacing 3.3 V or 5 V logic levels to higher-voltage devices. Packaged in the ubiquitous SOT-23 surface mount enclosure, it offers extremely low on-state resistance (R_DS(on)) at low gate voltages, which minimizes power losses and improves overall system efficiency. Therefore, you can reliably use this MOSFET for quick switching tasks in battery-operated and portable equipment.

Key Features:

• Low Threshold Voltage: The device features a low gate threshold voltage (V_GS(th) ≤ 1.5 V), which ensures direct logic-level drive capability from microcontrollers (MCUs) and other digital ICs.
• Low R_DS(on): Offers minimal on-state resistance (R_DS(on) typically 3.5 Ω @ V_GS=5V), reducing power dissipation and self-heating during switching.
• Fast Switching Speed: Operates at high frequencies due to low gate charge (Q_g), making it ideal for Pulse Width Modulation (PWM) applications.
• Compact SOT-23 Package: The tiny Surface Mount Technology (SMT) package is optimal for space-constrained and high-density PCB designs.
• High Reliability: Provides reliable performance across a wide junction temperature range (T_J up to +150°C).

Technical Specifications:

• Drain-Source Voltage (V_DSS): 50 V
• Continuous Drain Current (I_D): 200 mA (at T_A = 25°C)
• Pulsed Drain Current (I_DM): 800 mA
• Gate-Source Threshold Voltage (V_GS(th)): 0.8 V to 1.5 V
• Static Drain-Source On-Resistance (R_DS(on)): Typically 3.5 Ω (Max 6 Ω @ V_GS=5V)
• Power Dissipation (P_D): 350 mW (Max)
• Operating Temperature Range: −55°C to +150°C

Mechanical Specifications:

• Package Type: SOT-23 (Small Outline Transistor, 3-pin)
• Mounting: Surface Mount Device (SMD)
• Moisture Sensitivity Level (MSL): MSL 1 (Unlimited floor life)
• Package Material: Epoxy Encapsulation

Dimensions:

• Body Length (L): ≈ 2.9 mm
• Body Width (W): ≈ 1.3 mm
• Body Height (H): ≈ 1.0 mm
• Lead Pitch: ≈ 1.9 mm
• Weight: ≈ 8 mg (Extremely lightweight for high-volume manufacturing)

Pinout and Wiring:

• Pin 1 (Gate – G): Controls the current flow between the Drain and Source. Connect this pin to the microcontroller’s logic output.
• Pin 2 (Source – S): Connect this pin to the circuit ground (GND) or the return path of the circuit.
• Pin 3 (Drain – D): Connect this pin to the load, which connects to the positive voltage source (V_DD).
• Wiring Note: Remember to place a pull-down resistor on the Gate if the control pin might float during startup, ensuring the MOSFET remains safely off.

Datasheet Reference:

• Download ON Semiconductor BSS138 Datasheet

Commonly Used in:

• Logic Level Shifting/Translation: Essential for converting logic signals (e.g., 3.3V to 5V) in bidirectional data lines.
• Portable Devices: Used in smartphones, tablets, and wearables for power management and switching.
• I/O Port Protection: Provides an intermediate stage to protect sensitive MCU pins from higher voltage loads.

Applications:

• LED and Display Backlight Drivers: Quickly and efficiently switches small LED strings using PWM control.
• Small Motor Control: Drives miniature DC motors and solenoids that operate within the current limits.
• Signal Multiplexing: Works as a low-loss, fast analog switch in various data acquisition systems.
• Level Shifting Interfaces: Furthermore, the BSS138LT1 is a fundamental component for I²C and SPI bus level translation.

Equivalent Models:

• 2N7002: A popular, general-purpose N-Channel MOSFET in an SOT-23 package with similar V_DSS and I_D ratings.
• TNMOS BSS138: Functionally identical versions from other manufacturers, such as Nexperia or Infineon.
• SI2301: Offers slightly different specifications but serves as a common alternative in low-power SMT switching applications.

Package Includes:

• 1 x BSS138LT1 N-Channel Power MOSFET 200mA 50V SOT-23