| 摘要 |
PROBLEM TO BE SOLVED: To assure safety in operation of a portable telephone and a circuit where a field effect transistor (FET) is used. SOLUTION: When a negative voltage D comes to be 0V due to failure of a negative voltage generating circuit 39b, no bias voltage is applied to the gate electrode of the FET of a power amplifier 33. Then, an nMOS (n channel type MOSFET (metal oxide FET)) 44 comes to be an off state so that a drain electrode is opened. Since the gate electrode and the source electrode of a pMOS (p channel type MOSFET) 46 are at the same level due to a resistor 45, the pMOS46 comes to be an off state, resulting in shielding an inversion control signal J. Then, since the gate electrode and the source electrode of a pMOS47 come to be the same level due to a resistor 48, the pMOS47 comes to be an off state. So, applying of a positive voltage E to the drain electrode of the FET of the power amplifier 33 is stopped, thereby protecting the FET and the pMOS47. COPYRIGHT: (C)2005,JPO&NCIPI
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