| 摘要 |
PURPOSE:To obtain small size and light weight of an output transformer by providing a means applying once tone burst processing to a PWM wave, applying full-wave rectification to decode the PWM wave in a power amplifier for an electroacoustic transducer utilizing the pulse width modulation (PWM) wave so as to drive the electroacoustic transducer of the electrostriction type to be driven. CONSTITUTION:A sinusoidal VIN having the same low frequency as the drive frequency of an electroacoustic transducer 10, e.g., 3kHz is given to a noninverting terminal of a comparator 2 and a triangle wave Vosc having a frequency of a multiple, e,g. 10 times, that is, 30kHz is given to an inverting terminal from a triangle wave generator 3 respectively, and a PWM signal is obtained as A rectangular wave generator 4 outputs a prescribed frequency, e.g., 300kHz of sinusoidal wave VOUT only when the inputted PWM signal is positive. The voltage VOUT is a tone burst wave outputted as a 300kHz sinusoidal wave corresponding to the PWM signal pulse train of VCOMP. Thus, the output transformer 7 handles the frequency of 3kHz in a form of 300kHz tone burst wave and the size is decreased remarkably and the weight is decreased.
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