A transmitter includes a capacitor from one end of which a charge voltage is derived; a first constant current source to generate a charge current for the capacitor; a second constant current source to generate a discharge current for the capacitor; a charge/discharge controller to perform charge/discharge control of the capacitor based on a logic level of a transmission input signal and a comparison result between the charge voltage and a reference voltage; an output stage to generate the transmission output signal, wherein a slew rate of which is set in response to the charge voltage, and wherein an amplitude of the transmission output signal is set in response to an output side power source voltage; a reference voltage generator to fluctuate the reference voltage depend on the output side power source voltage; and a constant current controller to fluctuate a current value of the charge current and the discharge current depend on the reference voltage.