| 摘要 |
PROBLEM TO BE SOLVED: To suppress a waveform distortion by connecting an output impedance variable part between an output buffer and a signal line, varying the output impedance and controlling the output impedance in conformity with a timing of change in the detected output signal. SOLUTION: When an output signal state change detection part 4 monitors input to an output buffer 1 and detects that a signal value changes, it informs a continuous variable part 3 that the output impedance needs to be changed. The continuous variable part 3 generates a control signal and controls an output impedance variable part 2 when the information is received. This continuous control signal makes it possible for the output buffer 1 to supply a signal line 5 with a sufficient current at the point when the output signal starts to change, and rising of a signal becomes faster. Afterwards, it is controlled so that an impedance value of the output impedance variable part 2 gradually becomes high. Thus, a current value which can be supplied by the output buffer gradually decreases.
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