| 摘要 |
PROBLEM TO BE SOLVED: To provide a power amplifier which is inexpensive and small in power loss, and can reduce the influence of a produced noise. SOLUTION: On the basis of the source voltages VP and VQ and output signal SOUT of an amplification part, pulse width control circuits 23 and 43 generate driving signals SWA and SWB which are equal in frequency to a signal FS and varied in duty ratio on the basis of signals EVA and EVB to drive FETs 12 and 32. The source voltages±VIN are boosted corresponding to the signal SOUT and supplied to the amplification part 50. The signal FU from an oscillation circuit 66 has its frequency divided by a frequency divider 68 to generate a signal FS. With the signal BD from a frequency division control part 69, the frequency division ratio of the frequency divider 68 is varied continuously or noncontinuously. Thus, the frequency of the signal FS is varied and then the fundamental wave wave component and higher harmonic components of noise due to the switching of the FETs 12 and 32 are varied to reduce the noise of specific frequency per unit time.
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