| 摘要 |
<p>PURPOSE: To maintain the precision of a virgin cell for a long period and improve the reliability of the circuit by using the virgin cell which has characteristics shifted by a voltage shifter. CONSTITUTION: A cell and virgin cells 12 and 13 have gate-source voltages lower than a source voltage through voltage shifters 14 and 15 and their characteristics depend upon an operating load. In read mode, a logical signal R is low and a logical signal V is high, so switches 21, 26, 29, 33, and 40 are closed and a switch 42 is opened. When the source voltage is lower than 2.3V as the threshold voltage of the cells 12 and 13, the cells 11, 12, and 13 are turned off. When the source voltage exceeds it, the cells 12 and 13 turn on, but their characteristics become smaller than a logical slope because of the presence of the load. The cell 11 is off between 2.3V and the source voltage and then a current flows to neither a load transistor 18 nor a mirror transistor 23; and only the cell 12 has a high resistance value and a current is made to flow through a load transistor 30 for supply current limitation.</p> |
