US Patent 7180326 Noise elimination circuit

A noise elimination circuit sets a certain time period for eliminating noise occurring immediately after a change in the logic level of an input signal by a delay time of a first delay buffer. It also adjusts the timing of switching by delay times of second and third delay buffers. The noise elimination circuit thereby blocks the input signal for a certain period of time immediately after the change in the logic level of the input signal to keep a switching signal by a latch circuit or transmit only the same logic level as the input signal to an output.