| 摘要 |
An IrDA module is coupled to a tapped inductor and makes both IrDA and remote control (RC) transmissions. The IrDA module includes a transmitter LED and a field effect transistor (FET) switch. The inductor has a first lead, a second lead and a tap. The first lead is coupled to a battery voltage, and the tap is coupled through a resistor to the LED anode. The drain of the FET switch is coupled to both the LED cathode and the second lead of the inductor. The location of the tap on the inductor is chosen such that the voltage drop across the LED when the FET switch is turned on and before the inductor saturates results in a desired IrDA LED drive current without using current-limiting resistors that can dissipate power. After the inductor saturates, the voltage drop across the LED results in a larger RC LED drive current.
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