| 摘要 |
PROBLEM TO BE SOLVED: To provide a power amplifier circuit using a PWM modulation circuit that prevents variations of the circuit gain. SOLUTION: The PWM modulation circuit 10a comprises a comparator 11, and an integrator 20, whose integrated output is compared with an input signal from a signal source 16 via an amplifier 15 by the comparator 11 to produce a PWM signal having an advanced phase characteristic due to differentiation of the input signal. A switching circuit 21 amplifies the PWM modulation signal The amplified PWM modulation signal is supplied to a speaker 27 via an LC filter 26, and it is also negatively fed back to the input side of the PWM modulation circuit. In this case, a positive source voltage and a negative source voltage of the switching circuit 21 are respectively switched depending on an output of the comparator 11, and input terminals of the comparator 11 receives signals. Thus, variations in the circuit gain are prevented. COPYRIGHT: (C)2007,JPO&INPIT
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