| 摘要 |
PROBLEM TO BE SOLVED: To provide a power amplifier capable of maximally developing effects of a high efficiency, low heat generation and low distortion by smoothly switching power supplies in a power amplifier system employing multi-power-supplies. SOLUTION: The power amplifier includes: an input circuit 1; three power supply lines, that is, first, second and third power lines 11, 12, 13 which sequentially employ lower voltages; a push side drive circuit 2 and a pull side drive circuit 3 respectively receiving a control signal from the input circuit; three drive signal lines receiving outputs from the drive circuits; three output transistors M1, M2, M3 each one end of the conduction paths of which is respectively connected to the first, second, and third power lines and whose gates are respectively connected to the three drive signal lines; an output terminal 15 to which the other ends of the conduction paths of the output transistors are connected in common; an impedance circuit 4 for adjusting the gate impedance of the output transistor connected to the third power line; and a feedback circuit 5 connected between the output terminal and the input circuit. COPYRIGHT: (C)2006,JPO&NCIPI
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