PURPOSE: To control the transmission of a signal varied at a high speed with an external semi-fixed control signal without deteriorating its transmission characteristic by providing a capacitive element bypassing a switching element in terms of AC.

CONSTITUTION: A CMOS transistor(TR) Mn2 control signal transmission as a switching element. When the TR Mn2 is turned on in a steady-state and the transmission by TRs Mp1, Mn1 is implemented, the ON-resistance of the TR Mn2 is interposed in terms of DC between the TR Mn1 and a reference potential GND. However, the ON-resistance is bypassed by a capacitive element Cp in terms of AC, then a transient current to charge/discharge a transmission output of a logical signal to a high or a low level flows smoothly without being disturbed by the ON-resistance. Thus, the transmission of the signal changing at a high speed is controlled with an external semi-fixed control signal without deteriorating the transmission characteristic.