| 摘要 |
PURPOSE:To quicken a write operation, and to execute a storage operation at a high speed, by supplying a constant current to a digit line, and increasing a constant current value of a constant current source, at tie time of write operation. CONSTITUTION:Resistances R600, R601 which become a constant current source, and transistors Q600, Q601, Q602 and Q603 for switching a supply destination of a constant current and a constant current source are constituted. In this state, at the time of write operation, signals W0', W1' become a low level as write signals W0, W1 become a low level, the transistors Q600, Q601 become off, and the transistors Q602, Q603 become on. Accordingly, constant values IW0, IW1 flow to digit lines D0, D1 through the transistors Q602, Q603, are added to read-out currents IR0, IR1, and currents IW0, IW1 flow. In this way, discharge of parasitic capacity connected to the digit lines D0, D1 and an inverted operation of a cell are executed by an increased current value, therefore, the write operation is executed at a high speed. |
