A digital waveform conditioning circuit for restoring a deformed digital signal into its original rectangular waveform, comprising an input terminal supplied with the deformed digital signal, a circuit for generating a reference signal by combining positive and negative voltage components rectified from positive and negative cycles of the deformed signal, a comparator for comparing the deformed signal with the reference signal, a circuit for holding an output signal of the comparator for a period controlled by a clock signal for synchronizing the output signal with the original rectangular signal, and an output terminal for receiving the output of the holding circuit.