| 摘要 |
<p>PURPOSE:To measure the reliability of even a memory cell where the floating gate is electrified positively and the threshold voltage has a negative polarity, by supplying a prescribed voltage supplied from the external to a sense amplifier through a transistor TR as a reference voltage. CONSTITUTION:The drain of a dummy cell TR13 having the floating gate is connected to the source of a TR41 together with a load circuit 14. The gate of the TR41 is controlled by a bias generating circuit 50 connected to a voltage from an external terminal 51, and the external voltage from a terminal 42 is supplied directly to the TR13. Then, the reliability is tested on a basis of variance or nonvariance of the threshold of a memory cell TR11 having the floating gate according as the external voltage from the terminal 42 by which the output of a sense amplifier 25 is inverted at a normal temperature and that after leaving the memory cell at a high temperature for a long time are equal to each other or not. By this constitution, the reliability of even the memory cell where the floating gate is electrified positively and the threshold voltage has the negative polarity can be measured.</p> |
