| 摘要 |
PURPOSE:To improve the linearity and dynamic range by converting an input digital data into plural PWM waves with equal pulse width and symmetrical to the right and left within one converting period. CONSTITUTION:A serial data fed to a data input terminal 1 is converted into a parallel data at an S/P converter 2 and fed to a modulation control section 10. A high-order 2-bit is fed to a shift register 13 via a PAM decorder 15. Each output of the shift register 13 is fed to a switching control circuit 16. A low- order 3-bit of the parallel data is fed to a circuit comprising coincidence detection circuits 22, 23, a complement circuit 25, a flip-flop 26 and a counter 12 and converted into a PWM wave comprising 4 PWM pulses whose pulse width is changed symmetrically to the right and left around the timing of each center of each section dividing one converting period into equal intervals respectively. The data is converted into an analog signal by controlling a modulation section 30 with an output of the switching control circuit 16 and the PWM wave. |
