Abstract: The gate of a first P-channel transistor of a first comparator is supplied with an input signal, and the gate of a second P-channel transistor of the first comparator is supplied with a reference voltage. An output terminal of the first comparator is connected to an output circuit and the gates of first and second P-channel transistors of a second comparator are supplied with the reference voltage. The second comparator outputs a voltage equal to a stand-by time output voltage of the first comparator and the output voltage from the second comparator is supplied to the non-inversion input terminal of a third comparator which is connected to a voltage generating circuit. The voltage generating circuit has substantially the same dimension ratio as the output circuit and generates a voltage equal to the threshold voltage of the output circuit.

Abstract: A sense amplifier of this invention has a main characteristic feature in that it has low power consumption in an input waiting state, and can perform a highspeed sensing operation. The sense amplifier includes an output transistor, a constant current source connected between the base of the transistor and a first power source, a MOS transistor, having a source-drain path connected between the base of the transistor and a second power source, for receiving most of a current from the constant current source, and a load resistor for the transistor. The base potential of the output transistor in the input waiting state is set to be a value corresponding to a state immediately before or after the transistor is turned on.