Abstract: A voltage detection circuit outputs a detection signal when an amount of charges read to one of a pair of bit lines reaches a predetermined amount. A mask circuit of a timing generator masks an output of a sense amplifier activation signal until the detection signal is output. A sense amplifier determines logics of data read to the bit lines from memory cells in synchronization with the sense amplifier activation signal. An operation of the sense amplifier is started after predetermined amounts of charges are read from the memory cells to the bit lines, that is, after the detection signal is output. Accordingly, even when a timing to output a timing signal becomes early due to a variance of manufacturing conditions of a semiconductor memory, data read from the memory cells can be latched correctly in the sense amplifier. As a result, malfunctions of the semiconductor memory can be prevented.

Abstract: A fractional-N frequency synthesizer comprises a voltage-controlled oscillator (107) for generating an output signal (F.sub.o) in response to a control voltage derived by a digital-to-analog converter (105) from a digital error signal (e). The error signal is derived by a differencing device (103) which subtracts a digital signal (D.sub.o) representing the actuated frequency of the output signal from an input signal (F.sub.d) having the desired frequency for the output signal. The digital signal representing the output signal frequency is derived by a frequency discrimination device (101) which determines the instant frequency of the analog output signal and provides a corresponding digital representation with zero static frequency error. In preferred embodiments, the frequency discrimination device is a delta-sigma frequency synthesizer in combination with a decimator (102). This frequency synthesizer configuration avoids deficiencies due to non-linearity and noise sensitivity of analog phase detectors.