| 摘要 |
PURPOSE:To decrease the distortion and to realize the cost-down, by changing the duty ratio and frequency in response to the level of an input signal, in a pulse width modulation circuit used for audio signal amplification. CONSTITUTION:To a control input terminal of a voltage controlled oscillator 2a, a DC voltage Vc changed in proportion to a signal level of an audio signal ea is applied. Thus, the duty ratio and the frequency of an output signal ep of a pulse modulation circuit 2b outputted from a pulse amplifier 3 are changed in response to the signal level of the audio signal ea. Thus, the reduction in the required band and the distortion are attained. |
