Sense amplifier having a high operation speed and a low power consumption

A sense amplifier for use in a semiconductor memory having a plurality of memory cells, comprising:

• a first differential amplifier receiving a potential signal read out from a selected memory cell and a reference potential, and having an output for outputting a first differentially amplified output;
• a second differential amplifier receiving said potential signal read out from said selected memory cell and said reference potential, and having an output for outputting a second differentially amplified output amplified in a phase opposite to that of said first differential amplifier;
• a first inverter circuit composed of a first MOS transistor of a first conductivity type and a second MOS transistor of a second conductivity type opposite to said first conductivity type, said first inverter circuit having a threshold level corresponding to an intermediate level between a high logic level and a low logic level of binary information, said first inverter circuit having an input receiving said second differentially amplified output and an output for outputting an inverted signal of said second differentially amplified output;
• an amplifier circuit composed of a third MOS transistor of said first conductivity type having the same characteristics and the same size as those of said first MOS transistor and having a gate receiving said inverted signal of said second differentially amplified output so as to be on-off controlled by said inverted signal of said second differentially amplified output, and a fourth MOS transistor of said second conductivity type having the same characteristics and the same size as those of said second MOS transistor and having a gate receiving said first differentially amplified output so as to be on-off controlled by said first differentially amplified output, a drain of said third MOS transistor and a drain of said fourth MOS transistor being connected to each other so as to constitute a signal output node;
• a latch circuit having an input connected to said signal output node of said amplifier circuit and including a second inverter circuit having the same circuit construction and the same threshold level as those of said first inverter circuit and a transfer gate connected between said input of said latch circuit and an input of said second inverter circuit and on-off controlled by a control signal in such a manner that when said control signal is at a first level, said transfer gate transfers an output signal outputted from said signal output node of said amplifier circuit to said input of said second inverter circuit, and when said control signal is at a second level different from said first level, said latch circuit hold said output signal outputted from said signal output node of said amplifier circuit so as to cause said second inverter circuit to output a sense-amplified signal;
• and
• an equalizing circuit connected to said output of each of said first and second differential amplifiers, said input and said output of said first inverter circuit and said signal output node or said amplifier circuit, and controlled by said control signal so as to equalize a potential on said output of each of said first and second differential amplifiers, said input and said output of said first inverter circuit and said signal output node of said amplifier circuit when said control signal is at said second level.