| 摘要 |
PROBLEM TO BE SOLVED: To provide an envelope tracking power amplifier which can highly efficiently operate even if a signal with a high average-to-peak power ratio is inputted, and an envelope tracking amplification method. SOLUTION: A level comparator 16 compares the level of a signal inputted to an envelope amplifier 4 with a prescribed level. When the signal level is lower than the prescribed level, a power supply voltage is supplied from the envelope amplifier 4 to an RF amplifier 6, an input signal to an RF amplifier 12 is shut off, and control is performed for setting a drain voltage outputted from a drain voltage control circuit 15 in accordance with the signal level so that drain/source capacitance may reach a preset value. If higher than the prescribed level, the input signal is supplied to the RF amplifier 12, a bias of the gate voltage of the RF amplifier 2 is set so that the operation of the RF amplifier may be aligned with the RF amplifier 6, and the drain voltage control circuit 15 is set to fix the power supply voltage. COPYRIGHT: (C)2011,JPO&INPIT
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