| 摘要 |
PURPOSE: An audio apparatus is provided to reduce a consumption power and to elongate a use span of a battery with a high efficiency. CONSTITUTION: An audio apparatus comprises an R-channel audio signal output circuit(1),an L-channel audio signal output circuit(2) and a controller(10). The audio signal output circuit(1) comprises a bit shifter(3), a digital-analog converter(4), a pulse width modulation(PWM) switching power amplifier(5) and a filter circuit(6), and drives a headphone speaker(7). The bit shifter(3) has two input terminals(3a,3b) and an output terminal(3c). The bit shifter(3) receives a volume control signal(Vd) from the controller(10) through the input terminal(3b), and shifts a main signal(S) of eight bits through the input terminal(3a) upward by a digital value of the volume control signal(S) of three bits. The digital-analog converter(4) converts an output from the bit shifter(3) through the output terminal(3c) into an analog signal. The PWM switching power amplifier(5) receives the analog signal from the converter(4), and consists of a PWM pulse generator(5a) and a pulse oscillator(5b). The filter circuit(6) converts a PWM signal from the amplifier(5) into a current value corresponding to an amplitude of an analog signal.
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