| 摘要 |
PROBLEM TO BE SOLVED: To obtain a pulse width modulation circuit which raises the power efficiency of an envelope tracking power amplifier even when an electric power of a modulation signal input to the power amplifier is low. SOLUTION: The pulse width modulation circuit of the invention includes a first comparator 2 which compares a triangle wave carrier output from a triangle wave generation circuit 1 with an envelope signal and outputs the pulse width modulation signal, a second comparator 3 which compares the envelope signal with a threshold voltage V1 and outputs a control signal which switches the triangle wave generation circuit 1 ON/OFF, and a third comparator 4 which compares the envelope signal with a threshold voltage V2 higher than the threshold voltage V1 and outputs a control signal which switches the first comparator 2 ON/OFF, and generates the pulse width modulation signal. COPYRIGHT: (C)2011,JPO&INPIT
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