M21X-VB is a P-Channel field effect transistor of VBsemi brand. The specific parameters are as follows:
- Package: SOT23
- Maximum operating voltage: -20V
- Maximum current: -4A
- RDS(ON): 57mΩ @ VGS=4.5V, VGS=12V
- Threshold voltage: Vth=-0.81V

**Application introduction:**
Suitable for circuits and modules that require P-Channel MOSFET, especially in situations where lower impedance and smaller threshold voltage are required.

**Example application:**
1. **Power management module:** Due to low impedance and moderate current capacity, it is suitable for power switch and regulation modules.

2. **LED drive:** In LED drive circuits that require reverse control, M21X-VB can be used.

3. **Battery protection circuit:** Due to the small SOT23 package and low threshold voltage, it is suitable for battery protection circuit to ensure that the battery is cut off in low voltage state.

Please note that the specific application needs to be verified according to the electrical requirements and design parameters of the project.