PURPOSE: To suppress the unnecessary switching of an output driver according to the initialization of a differential amplifier by providing an inverter on the poststage of the differential amplifier and controlling an input logical threshold value based on a logical voltage state of an output terminal.

CONSTITUTION: The output signal O of the output driver 4 is inputted to an output detection circuit 8, and the logical threshold value of the inverter 5 is controlled by the output signal S1 of the circuit 8. When the remaining data of a data line D before the initialization and the read-out data are a LOW level also, the LOW level is held by the output O of the output driver 4 continuously. Further, when the voltage of the output terminal P before the initialization by an initializing signal () is a HIGH level, the output signal S1 of the output detection circuit 8 becomes the HIGH level, and a transistor TP1 is turned off, and thus, the input threshold value of the inverter 5 is lowered, and the HIGH level before the initialization is held by the output signal O. Thus, the switching of the output driver according to the initialization of the differential amplifier is suppressed, and power consumption and a power source/ground noise are reduced.