I'm working on a circuit using an **IRLML6402 P-channel MOSFET** to control power to a **Capacitive Soil Sensor V2.0**. The schematic is attached.
### **Expected Behavior:**
When the MOSFET is supposed to be off, I expect the **Vcc** pin of the soil sensor to be **0V**.
### **Observed Issue:**
Instead of 0V, I measure **1.1V** at the **Vcc** pin when the MOSFET should be off.
### **Key Circuit Details:**
- **Source (Pin 2)** is connected to **+3.3V**.
- **Gate (Pin 1)** is controlled via a **2.2kΩ pull-down resistor (R3)** and a **4.7µF capacitor (C4)**.
- **Gate-Source voltage should be 0V when off**, but the MOSFET seems to still conduct slightly.
### **Questions:**
1. **Why is the MOSFET not fully turning off?** Could there be leakage current causing this?
2. **What could be the reason for the unexpected 1.1V at the sensor's Vcc?**
3. **Is the gate pull-down resistor (2.2kΩ) too weak, or is the capacitor affecting turn-off time?**
4. **Should I try a stronger pull-down resistor or another MOSFET with a lower threshold voltage?**
Any insights would be greatly appreciated! Thanks in advance.
### **Expected Behavior:**
When the MOSFET is supposed to be off, I expect the **Vcc** pin of the soil sensor to be **0V**.
### **Observed Issue:**
Instead of 0V, I measure **1.1V** at the **Vcc** pin when the MOSFET should be off.
### **Key Circuit Details:**
- **Source (Pin 2)** is connected to **+3.3V**.
- **Gate (Pin 1)** is controlled via a **2.2kΩ pull-down resistor (R3)** and a **4.7µF capacitor (C4)**.
- **Gate-Source voltage should be 0V when off**, but the MOSFET seems to still conduct slightly.
### **Questions:**
1. **Why is the MOSFET not fully turning off?** Could there be leakage current causing this?
2. **What could be the reason for the unexpected 1.1V at the sensor's Vcc?**
3. **Is the gate pull-down resistor (2.2kΩ) too weak, or is the capacitor affecting turn-off time?**
4. **Should I try a stronger pull-down resistor or another MOSFET with a lower threshold voltage?**
Any insights would be greatly appreciated! Thanks in advance.