**Application fields:**
BSS138K-VB is commonly used in the following fields and modules:

1. **Low-power electronic devices:** Due to its low drain-source resistance and low threshold voltage, it is often used in low-power electronic devices such as portable devices, sensors, and battery-driven devices.

2. **Signal switch:** This model is also often used as a signal switch, such as a switch circuit in analog and digital circuits to achieve signal switching and control.

3. **Small power management:** BSS138K-VB can be used in small power management modules such as battery charging and power supply selection.

4. **Sensor interface:** In the sensor interface circuit, it can be used to control the operation and data acquisition of the sensor.

It should be noted that the specific application field may vary depending on the product use, circuit design, and specification requirements. When selecting and using this model, it is recommended to determine its applicability based on the electrical characteristics and performance requirements of the specific application. This device is suitable for applications that require compact size and low power consumption.