Abstract: A waveform shaping circuit which shapes an input signal into an output signal having a rectangular waveform. The waveform shaping circuit according to the present invention includes a first MOS transistor having a first terminal to which said input signal is applied, a second MOS transistor having an second terminal for supplying an output signal and a third terminal connected to ground an impedance element which is connected between a second terminal of said first MOS transistor and a first terminal of said second MOS transistor, a reference voltage source which is connected between a third terminal of said first MOS transistor and ground, and a third MOS transistor having a second terminal which is connected to the third terminal of said first MOS transistor and a first terminal which is connected to the second terminal of said second MOS transistor and a third terminal which is connected to ground.