BSS138P Detailed explanation of pin function specifications and circuit principle instructions

The BSS138 P is a specific N-channel MOSFET manufactured by ON Semiconductor (previously Fairchild Semiconductor). It is typically used for low-power switching applications.

Package:

The BSS138P is most commonly found in the SOT-23 package, which is a small surface-mount package with three pins.

Pin Function Specifications and Circuit Principle:

The BSS138P MOSFET is a 3-pin device, and each pin has a specific function:

Gate (G): Pin 1 (G) controls the MOSFET switching behavior. Applying a voltage to the Gate pin allows current to flow between the Drain and Source. It is typically connected to the control signal in a circuit. Drain (D): Pin 2 (D) is where the load current flows through when the MOSFET is on. In typical switching applications, the Drain is connected to the load. Source (S): Pin 3 (S) is where the current returns to ground or a lower potential when the MOSFET is conducting.

Pinout Table (SOT-23 Package):

Pin Number Pin Name Function Description Pin 1 Gate (G) The gate controls the MOSFET switching by applying a voltage to this pin. Pin 2 Drain (D) The drain is where the current flows from the MOSFET when it is switched on. Pin 3 Source (S) The source is where the current returns to the circuit ground when the MOSFET is conducting.

FAQ:

1. What is the BSS138P MOSFET used for? The BSS138P is an N-channel MOSFET, commonly used for low-power switching applications, such as level shifting, power control, and switching regulators. 2. What is the maximum Gate-Source voltage for BSS138P? The maximum Gate-Source voltage for the BSS138P is ±20V. Exceeding this voltage can damage the MOSFET. 3. What is the drain-source voltage rating of the BSS138P? The BSS138P can handle a maximum Drain-Source voltage (Vds) of 50V. 4. What is the maximum continuous drain current for the BSS138P? The maximum continuous drain current for the BSS138P is 220mA at a temperature of 25°C. 5. How do I calculate the on-resistance of the BSS138P? The on-resistance (Rds(on)) of the BSS138P is typically around 3Ω when Vgs is 10V. 6. What is the gate threshold voltage for BSS138P? The gate threshold voltage (Vgs(th)) for the BSS138P is between 1.3V and 3V. It is the voltage at which the MOSFET begins to turn on. 7. Can I use the BSS138P in a high-power application? The BSS138P is designed for low-power applications and is not suitable for high-power switching because of its limited current and voltage handling capabilities. 8. What are the advantages of using the BSS138P MOSFET? The BSS138P is small, has low on-resistance, and can be used for low-power switching applications in circuits like level shifters and small signal switches. 9. What is the maximum power dissipation of the BSS138P? The maximum power dissipation for the BSS138P is typically around 250mW when the device is operating at room temperature. 10. Can the BSS138P be used for switching inductive loads? No, the BSS138P is not recommended for switching inductive loads due to the possibility of voltage spikes generated by inductance that could damage the MOSFET. 11. What is the gate capacitance of the BSS138P? The BSS138P has a typical gate capacitance (Cgs) of 8pF, which can affect switching speeds in high-frequency circuits. 12. What is the typical gate charge of the BSS138P? The typical gate charge (Qg) for the BSS138P is 10nC at Vgs = 10V. 13. What is the Rds(on) at different gate voltages? At Vgs = 10V, Rds(on) is typically around 3Ω. At Vgs = 4.5V, it can be higher due to lower gate drive. 14. Can I use BSS138P in a 3.3V logic system? Yes, the BSS138P can work in a 3.3V logic system, but it may not fully turn on unless the Gate voltage is sufficiently high (e.g., 4.5V or more for efficient operation). 15. How do I drive the gate of the BSS138P? The gate of the BSS138P is driven by applying a voltage relative to the Source pin. A higher gate voltage (greater than Vgs(th)) will turn on the MOSFET. 16. What are the package sizes for the BSS138P? The BSS138P is commonly available in the SOT-23 package, a small 3-pin surface-mount package. 17. Is there a P-channel version of the BSS138P? No, the BSS138P is an N-channel MOSFET. There are different part numbers for P-channel MOSFETs with similar characteristics. 18. What is the difference between BSS138P and other MOSFETs? The main difference lies in the voltage and current ratings, as well as the threshold voltage, on-resistance, and the application suitability. 19. How do I protect the BSS138P in a circuit? Use a current-limiting resistor on the Gate and consider using a clamping diode for additional voltage protection, especially in circuits with high voltages. 20. Where can I find the datasheet for the BSS138P? You can find the detailed datasheet for the BSS138P on the ON Semiconductor website or through various distributor websites like Digi-Key or Mouser.

This explanation includes all the critical specifications and frequently asked questions about the BSS138P MOSFET.