| 摘要 |
<p>PURPOSE:To efficiently select either of a high-seed action mode or a low energy consumption mode by controlling a current supplied to a bit line by means of a mode setting signal. CONSTITUTION:N1 and N2 are made into nMOS transistors, P1-P4 are made into pMOS transistors, and the gate widths of the P1 and P2 are made into Wp1 and Wp2, respectively. When a control signal impressed to a control signal terminal 1 is made into '1', a current i1 at the primary side of a current mirror circuit is made into a steady value by being specified by means of the characteristics of the P1 and N1. When the gate lengths and gate widths of the transistors N1 and N2 are made equal, in case the mode setting signal is '0', the transistor P4 is turned off, and the current of i2=Wp2/Wp1.i1 is supplied to a bit line 3. When the mode setting signal is '1', the P4 is turned on. At the time of the on-resistance of the P3=the on-resistance of the P2, the current of 2Wp2/Wp1.i1 is made to flow to the bit line. Consequently, a reading from a memory cell is made high-speed in comparison to the case where the P3 is off. In such a way, either of the high-speed mode or low energy consumption mode can be selected.</p> |
