The invention provides a high speed sense amplifier of the current detection type employing NPN transistors used for a static operation type RAM which allows high integration and can suppress increase of power dissipation and deterioration in speed even in a high integration condition. Pairs of bit lines to which data of memory cells of a static type RAM are connected are connected to a pair of common data lines through MOS transistors, and the emitter terminals of a pair of bipolar transistors are connected to the data lines while the collector terminals which serve as signal output terminals of the sense amplifier are connected to a first power supply through resistors and the base terminals are connected to a second power supply. Further, a pair of resistance elements for normally supplying current to the sense amplifier therethrough are connected to the emitter terminals of the bipolar transistors.