To keep the constant pulse width despite the variance of the temperature and power voltage and also the individual differences of electronic parts by producing an alternating pulse signal having the pulse width almost equal to that of an output data signal and controlling variably the pulse width of the output data signal via a control signal that is in accordance with the pulse width of the alternating pulse signal.

The pulse width is controlled to obtain a pulse of an integral multiple of unit width in a high and low level periods of the output data respectively. Under such conditions, a pulse width reproduction circuit M1 generates an alternating pulse signal which alternates between 0 and 1 from an output data signal in a period double as much as the unit width and has the pulse width almost equal to that of the output data. A control signal generation circuit M2 generates a control signal that is in accordance with the pulse width of the alternating pulse signal. Based on this control signal, a pulse width control circuit M3 variably controls the pulse width of the output data signal. As a result, the pulse width of the output data signal is controlled at a constant level despite the variance of the temperature and power voltage and also the individual differences of electronic parts.