![]() Therefore, we can simplify the above formula to:Ī few words about the Gate resistor R G. The voltage drop across the sensing resistor is always 0.7, because the BJT transistor will not let the voltage drop to go higher than the V BE. The voltage across the MOSFET is calculated with this formula: Like before, the power dissipation on the MOSFET is calculate by the voltage across the Drain-Source multiplied with the current. ![]() This value is derived from the transistor's V BE contact. The Voltage portion of the previous formula is always 0.7 Volts. To choose an R S resistor you only need to solve this formula: The calculations for this circuit are very simple. Therefore, the current through the LED is regulated to the one defined by the resistor R S. This will pull the MOSFET's gate to the ground turning it off. When this voltage drop reaches the base-emitter voltage of the transistor (V BE=0.7V), the transistor is turned on. As current increases, the voltage drop across R S is increased as well. This allows current to run through the LED, the MOSFET and the sensing resistor R S. When power is applied, the gate resistor R G turns on the MOSFET. If you've learned how the single transistor driver works, then this circuit is very simple to understand.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |