PURPOSE: To obtain a semiconductor storage having a sense amplifier with circuit constitution where a main sense transistor hardly saturates and capable of operating at high speed with low voltage.

CONSTITUTION: Sense current flow through bit lines BL, BL' by presense transistors 1a, 1b. The collectors of current supply transistors 2a, 2b are connected directly to power source VCC, and a reference voltage Vref is inputted to respective bases. Constant current sources 3a, 3b are connected to respective emitters of the transistors 2a, 2b, and the sense current is supplied from respective emitters to the transistors 1a, 1b. The main sense transistors 5a, 5b are emitter connected, and the constant current source 6 is connected to both emitters. Resistors R1, R2 are connected between respective collectors of the transistors 5a, 5b and the power source VCC, and the emitter potential of the transistors 2a, 2b are inputted to respective bases. Output voltages Vout, Vout' are outputted from respective collectors of the transistors 5a, 5b.