By differentiating and using the signal that makes reference potential generation circuit become active (differentiating pulse generation block 1), and by operating the reference potential generation circuit for a certain period of time, the current consumption can be reduced in proportion to the frequency when the operation frequency is low. Also, unstable operation during high speed operation of the memory is prevented by using the differentiating pulse generation block 1 when the pulse width of an input signal is long, and by using a clock that is generated through an oscillator when the pulse width of the input signal is short.