BSS138LT1G-VB - 50V 200mA N-Channel MOSFET | VBsemi
MPN: BSS138LT1G-VB ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.05 | $0.05 |
| 10 | $0.042 | $0.42 |
| 100 | $0.0311 | $3.11 |
| 500 | $0.0265 | $13.25 |
| 1,000 | $0.0228 | $22.80 |
| 3,000 | $0.0195 | $58.50 |
Drop-in alternatives for BSS138LT1G-VB — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
BSS138LT1G
✅ Drop-In✓ In Stock
$0.08 / Unit
View Datasheet →BSS138W
✅ Drop-In📋 Reference alternative (not in catalog)
BSS138NH6327XTSA2
✅ Drop-In✓ In Stock
$0.15 / Unit
View Datasheet →2N7002LT1G
✅ Drop-In✓ In Stock
$0.02 / Unit
View Datasheet →NTR4003
✅ Drop-In📋 Reference alternative (not in catalog)
BSS138LT1G-VB Maximum Ratings & Electrical Characteristics
| Transistor Type | N-Channel Enhancement Mode MOSFET |
| Drain-Source Voltage (Vdss) | 50 V |
| Continuous Drain Current (Id) | 200 mA (Ta) |
| Power Dissipation (Pd) | 225 mW (Ta) |
| Mounting Type | Surface Mount |
| Package | SOT-23-3 (TO-236) |
| Configuration | Single FET |
| RoHS Status | Compliant |
| Manufacturer | VBsemi Elec |
| Equivalent To | onsemi BSS138LT1G |
BSS138LT1G-VB Pin Configuration
| Pin 1 | G — Gate - logic-level control input |
| Pin 2 | S — Source - connected to ground in low-side configurations |
| Pin 3 | D — Drain - connects to the switched load |
Safe Operating Area (SOA) & Thermal Characteristics
No official SOA curve available for this component. Always operate within absolute maximum ratings specified in the datasheet. Ensure adequate cooling and derate as needed.
Typical Applications
BSS138LT1G-VB is suitable for 6 applications: Low-Side Load Switching in Battery-Powered Products, Logic-Level Translation (5V <-> 3.3V), DC-DC Converter Auxiliary Switching, Relay and Solenoid Low-Side Drivers, LED Indicators and Backlight Strings, Power Management in Portable and Handheld Products.
Low-Side Load Switching in Battery-Powered Products
The BSS138LT1G-VB fits battery-powered load switching because its logic-level gate threshold turns on fully from a single lithium cell or 3.3 V regulator output, while the 50 V drain rating gives wide margin on 12 V rails. Used as a low-side switch, the source ties to ground and the load connects between the supply and the drain; a 100 kohm gate-to-source pulldown keeps the FET off during MCU reset. Its 200 mA continuous rating covers LEDs, buzzers, small relays, and sensor rails. Because the gate draws no DC current, the switch adds essentially zero quiescent drain - a key benefit for always-on battery products, though switching speed should be limited by a series gate resistor to control inrush and ringing.
Recommended
Logic-Level Translation (5V <-> 3.3V)
For open-drain buses such as I2C, the BSS138LT1G-VB is the canonical bidirectional level shifter: the gate ties to the low-voltage rail (3.3 V), the source to the 3.3 V pull-up line, and the drain to the 5 V pull-up line. When neither side drives, the body diode conducts and both lines settle at the lower rail; a low input then pulls the opposite side down through the channel. The MOSFET's low threshold guarantees full enhancement at 3.3 V gate bias, and its low gate charge minimizes capacitive loading on the bus. Pull-up resistors of 2.2 kohm to 10 kohm set rise times; the 200 mA rating vastly exceeds I2C sink currents, giving large reliability margin.
Recommended
DC-DC Converter Auxiliary Switching
The BSS138LT family is specified by onsemi for DC-DC converter applications, and the VBsemi equivalent inherits that role. Typical uses include switching the enable or sync input of a converter, gating a bias rail before the main switch, or acting as a small synchronous element in low-current buck circuits. The device's low input capacitance permits direct drive from PWM controller logic outputs with fast transitions and minimal drive loss, and the 50 V rating safely covers 24 V input topologies with transient margin. Designers should verify that average current including inductor ripple stays below 200 mA and that the 225 mW dissipation limit is respected at the converter's maximum ambient temperature.
Recommended
Relay and Solenoid Low-Side Drivers
Small signal relays in telecom, test equipment, and appliance control boards typically draw 20 mA to 150 mA coil currents at 5 V to 24 V - squarely within the BSS138LT1G-VB's 200 mA and 50 V envelope. The FET is wired low-side with the coil between the supply and the drain; a flyback diode across the coil clamps the inductive kick that would otherwise exceed the drain rating, and a 1 kohm gate resistor isolates the MCU pin from gate ringing. Its logic-level gate means no driver stage is needed. For larger solenoids, step up to a power MOSFET package such as SOT-223 or DPAK, since 225 mW dissipation bounds this device's continuous duty.
Recommended
LED Indicators and Backlight Strings
Low-current LED indicators and small backlight strings are ideal loads for the BSS138LT1G-VB in low-side drive configuration. A series resistor sets LED current; the MOSFET switches the cathode side, so either GPIO polarity or PWM dimming is trivially implemented with logic-level drive. The 50 V rating allows series LED chains well beyond 5 V rails, and the 200 mA current limit suits indicator clusters and small 0402/0603 LED arrays. Because PWM dimming toggles the gate capacitively, keep the series gate resistance near 100 ohm for crisp edges at kilohertz PWM frequencies. Power dissipation in the FET is minimal since the LED resistor, not the switch, drops the load voltage.
Recommended
Power Management in Portable and Handheld Products
onsemi targets the BSS138L at power management in portable and battery-powered products such as computers, printers, PCMCIA cards, and cellular and cordless telephones; the BSS138LT1G-VB serves the same design space at lower cost. Typical roles include gating peripheral power rails under software control, switching between battery and USB power paths at low current, and discharging output capacitors during shutdown. The SOT-23 footprint occupies under 3 mm by 3 mm of board area, critical in wearables and phone-style layouts. Designers should confirm leakage specifications for rail-keeping applications and verify the gate pulldown keeps the switch firmly off in deep-sleep states where GPIO floats.
Recommended
Recommended Products Summary
Engineering reference data for BSS138LT1G-VB — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | BSS138LT1G | BSS138W | BSS138 | 2N7002LT1G | NTR4003 |
|---|---|---|---|---|---|---|
| Package | SOT-23-3 (TO-236) | SOT-23-3 (TO-236) - same | SOT-23-3 (TO-236) - same | SOT-23-3 (TO-236) - same | SOT-23-3 (TO-236) - same | SOT-23-3 (TO-236) - same |
| Brand | VBsemi Elec | onsemi | onsemi | NXP Semiconductors | onsemi | onsemi |
| Vdss | 50 V | 50 V | 50 V | 50 V | 60 V | [DATA_NEEDED] |
| Continuous Drain Current | 200 mA (Ta) | 200 mA (Ta) | [DATA_NEEDED] | 220 mA class | [DATA_NEEDED] | [DATA_NEEDED] |
| Power Dissipation | 225 mW (Ta) | 225 mW (Ta) | [DATA_NEEDED] | [DATA_NEEDED] | [DATA_NEEDED] | [DATA_NEEDED] |
| Gate Threshold (Logic Level) | Low (logic-level) | Low (logic-level) | Low (logic-level) | Low (logic-level) | Higher threshold - not ideal at 3.3 V | Low (logic-level) |
| Unit Price Reference | $0.0311 (LCSC, qty 100, as of 2026-09-13) | Higher (DigiKey/Mouser) | [DATA_NEEDED] | [DATA_NEEDED] | [DATA_NEEDED] | [DATA_NEEDED] |
| Pinout (SOT-23) | 1=G, 2=S, 3=D | 1=G, 2=S, 3=D | 1=G, 2=S, 3=D | 1=G, 2=S, 3=D | 1=G, 2=S, 3=D | 1=G, 2=S, 3=D |
Key Differentiators
- Significantly lower unit cost than the original (vs BSS138LT1G)
- True logic-level threshold for 3.3 V drive (vs 2N7002LT1G)
- Identical footprint to the entire BSS138/2N7002 SOT-23 ecosystem (vs BSS138W)
Design Notes
The 200 mA rating is specified at 25 C ambient; dissipation must be derated above that temperature because total package power is capped at 225 mW at Ta. Estimated: at 50 C ambient with a typical SOT-23 derating near 1.8 mW/C, allowable dissipation falls to roughly 190 mW - keep continuous load current and RDS(on) losses well under this margin. Inductive loads without a flyback diode can spike the drain past 50 V and destroy the device; always clamp coils.
Place the SOT-23 with generous copper on the drain pad if switching near the 200 mA limit, as the small pads are the primary heat path. Keep the gate trace short and add a 100 kohm gate-to-source pulldown so the FET stays off when the MCU is in reset or the GPIO is high-impedance. A series gate resistor of 100 ohm to 1 kohm damps ringing when driven from fast logic, at a small cost in switching speed - negligible for load-switch duty cycles.
When using the BSS138LT1G-VB as an I2C or bidirectional level shifter, the MOSFET's body diode and gate-capacitance determine bus rise/fall behavior. Choose pull-up resistors (typically 2.2 kohm to 10 kohm) that meet the bus rise-time requirement at the target bus speed; a 3.3 V gate bias fully enhances the channel so the low-level voltage is set by RDS(on) times sink current, which is only a few millivolts at I2C currents. Verify threshold distribution at your actual gate voltage from the VBsemi datasheet.
Compliance Information
RoHS compliance inferred from the G suffix convention of the emulated BSS138LT1G and current VBsemi production standards. REACH, halogen-free, and conflict-minerals status must be confirmed with VBsemi documentation.
