| 摘要 |
PROBLEM TO BE SOLVED: To provide a headset interface circuit capable of automatically switching the amplification degree of a transmitter circuit according to the kind of a headset, and capable of operating at a voltage equal to or lower than a power supply voltage of a communication device. SOLUTION: A comparator 191 which is operated at a voltage equal to or lower than the power supply voltage 3.3 [v] is used for detecting an operation current of the transmitter 16t of the headset 16. Thus, a headset interface circuit 17 can be operated at a voltage equal to or lower than the power supply voltage 3.3 [v]. Furthermore, a decoupling capacitor C9 with one step is switched to decoupling capacitors C3, C9 with two steps according to the operation current of the transmitter 16t of the detected headset 16 so that noise mixture from the power supply V1 can be prevented depending on the kind of the connected headset 16. COPYRIGHT: (C)2011,JPO&INPIT
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