PURPOSE: To easily change the duty ratio at the output terminal of a pulse signal by varying the resistance value of a variable resistor in the output circuit of the pulse signal composed of a semiconductor integrated circuit or the like.
CONSTITUTION: When the signal waveform of an input pulse A fed to an input terminal 1 rises, 1st and 2nd P-channel MOS TRs 2, 4 are turned on and an N-channel MOSTR 3 is turned off. When the input pulse A descends, the TRs 2, 4 are turned off and the TR 3 is turned on. Third and 4th P-channel MOS TRs 6, 7 are always turned on and a gate voltage of the TR 6 is the division of a power supply voltage fed between a positive power terminal 5 and a negative power terminal 10 by an output impedance of the TR 7 and a variable resistor 11. Thus, when the resistance of the resistor 11 is increased, the gate- source voltage of the TR 6 is decreased and the driving capability is reduced. When the resistance of the resistor 11 is decreased conversely, since the gate- source voltage of the TR 6 is increased, the driving capability is increased.