| 摘要 |
<p>PURPOSE:To measure the threshold voltage of a memory element which is in write state at another sense level by reading changes in threshold voltage of the memory element at a prescribed sense level. CONSTITUTION:The sense level is set at the read by a comparison potential generation circuit REF by increasing a voltage VREF higher than the threshold value of a N channel MOSFET TR4 and lower than the threshold value of the TR4 in checking the threshold voltage of the memory element. In checking the threshold value, when the voltage at the input terminal IN is lower than the logical threshold value of the inverter comprising TR5, TR6, the TR2, TR1 are conductive and a current I1 flows. Then a minute current Ir1 flows to a high resistor R1 from the TR2 forming a current mirror by the TR1. In this case, the gate voltage of the memory element is slightly higher than the threshold voltage, the possibility of destruction of the TRs due to high voltage is prevented to measure the threshold voltage.</p> |
