The BSS138 LT1G is a specific model of a N-channel MOSFET transistor . It is manufactured by ON Semiconductor, a well-known semiconductor company. The BSS138LT1G is commonly used in a variety of low-voltage applications such as switching and amplification circuits.
Key Information:
Model: BSS138LT1G Brand: ON Semiconductor Package Type: SOT-23 (3-lead)Pinout & Functionality:
Here’s the detailed pinout for the BSS138LT1G:
Pin Number Pin Name Function 1 Drain Drain (D): This is the terminal where current exits the MOSFET. It connects to the load. 2 Gate Gate (G): This terminal controls the switching of the MOSFET. A voltage applied to this pin turns the MOSFET on. 3 Source Source (S): This is the terminal where current enters the MOSFET. It is connected to ground (for N-channel MOSFET).Pin Function Explanation:
Drain (Pin 1): The Drain pin is where the current flows out of the MOSFET. In an N-channel MOSFET like the BSS138LT1G, the drain is typically connected to the load or the circuit that is to be controlled. When the MOSFET is turned on, the current flows from the Source to the Drain. The voltage drop across the drain is important in switching circuits to ensure proper operation. Gate (Pin 2): The Gate pin controls the MOSFET’s on/off state. A positive voltage applied to the Gate relative to the Source pin will turn the MOSFET on, allowing current to flow between the Source and Drain. The voltage threshold (V_GS(th)) is typically 1.3V to 3V, meaning if the Gate-to-Source voltage is above this threshold, the MOSFET will be on. Source (Pin 3): The Source pin is connected to the ground or the lower potential side of the circuit for an N-channel MOSFET. Current enters the MOSFET through the Source terminal when the MOSFET is conducting. In the off state (when the Gate is not sufficiently positive), no current flows from the Source to the Drain.Circuit Principle:
In a typical circuit using the BSS138LT1G MOSFET, the Drain is connected to the positive voltage side of the load, while the Source is connected to the ground or negative side. The Gate is used to control the flow of current between the Source and Drain. When the Gate voltage exceeds the threshold voltage (V_GS(th)), the MOSFET enters its "on" state, allowing current to flow from Source to Drain.
20 FAQ - Common Questions about BSS138LT1G:
1. What is the maximum voltage rating for the BSS138LT1G?
The BSS138LT1G has a maximum Drain-to-Source voltage (V_DS) rating of 50V.2. What is the maximum current rating for the BSS138LT1G?
The maximum current (I_D) for the BSS138LT1G is 200mA.3. How do I use the Gate to control the MOSFET?
To switch the MOSFET on, apply a voltage greater than the threshold voltage (typically between 1.3V to 3V) to the Gate pin.4. What is the threshold voltage for the BSS138LT1G?
The threshold voltage (V_GS(th)) is typically between 1.3V and 3V.5. Can the BSS138LT1G be used for power switching?
Yes, it is suitable for low-power switching applications where current does not exceed 200mA.6. What is the maximum power dissipation for the BSS138LT1G?
The maximum power dissipation for the BSS138LT1G is 500mW at 25°C.7. How do I calculate the Gate current in a BSS138LT1G?
The Gate current is very low because the Gate of a MOSFET is capacitively charged. Typically, the Gate current is calculated using the capacitance and switching frequency.8. Can I use the BSS138LT1G for switching high current loads?
No, this MOSFET is designed for low current switching (up to 200mA). For higher currents, a MOSFET with a higher current rating should be used.9. Is there a specific use for the BSS138LT1G in logic circuits?
Yes, the BSS138LT1G is often used in logic level shifting, particularly in low-power logic circuits.10. How do I ensure the MOSFET stays off?
To turn off the MOSFET, ensure that the Gate voltage is below the threshold voltage (typically 1.3V to 3V), or connect the Gate to the Source to pull it to the same potential.11. What is the recommended operating temperature for the BSS138LT1G?
The BSS138LT1G is rated for an operating temperature range of -55°C to 150°C.12. What is the typical R_DS(on) for the BSS138LT1G?
The R_DS(on) (drain-to-source on-resistance) for the BSS138LT1G is typically 3Ω when the Gate-to-Source voltage is 10V.13. What is the Gate capacitance for the BSS138LT1G?
The Gate capacitance is typically around 3.5pF (at VDS = 25V, VGS = 0V).14. Can the BSS138LT1G be used for high-speed switching?
The BSS138LT1G is designed for low-speed switching. For high-speed switching applications, consider a MOSFET with faster switching characteristics.15. Is the BSS138LT1G suitable for motor control?
No, the BSS138LT1G is not suitable for motor control applications due to its low current rating.16. What is the gate threshold voltage range?
The Gate threshold voltage (V_GS(th)) range is typically 1.3V to 3V.17. How do I calculate the Gate drive resistance?
The Gate drive resistance depends on the Gate capacitance, desired switching frequency, and how fast you want to turn the MOSFET on/off. Generally, it is calculated based on the RC time constant.18. Can the BSS138LT1G be used in automotive circuits?
Yes, it can be used in low-voltage automotive circuits, as long as the current is within the 200mA limit.19. What is the typical switching time for the BSS138LT1G?
The typical switching time is in the range of 10ns to 50ns.20. How do I protect the BSS138LT1G from damage?
To protect the BSS138LT1G, ensure that the Drain-to-Source voltage and Gate-to-Source voltage do not exceed the specified maximum ratings. Use current-limiting resistors where appropriate.Let me know if you need more details!
