| 摘要 |
PURPOSE:To obtain a nonvolatile RAM whose information contents are not erased even when its source voltage drops or is cut off by using two nonvolatile semiconductor memory elements with floating gates for a bistable circuit and storing the information contents in the nonvolatile semiconductor memory elements. CONSTITUTION:Output information of the RAM are written in nonvolatile semiconductor memory elements Ma1 and Ma2 by holding VS at ''open'' and X1 at the ground potential, setting VCG to 15V, and varying VPP from 5V to 30V. The Ma2 is impressed with 30V at the drain and with 15V at the VCG to perform the writing operation. Consequently, the VT of the Ma2 is at -5V. On the other hand, the Ma1 has the drain held at 0V and VCG at 15V and its electric field is opposite in direction to the Ma2, so the VT of the Ma1 rises to +10V. Namely, erasing operation is performed. Thus, the writing and erasure are carried out at the same time. Then, the VPP and VS are raised from 0V to 5V to read the information back to the RAM. At this time, the VCG is set to 0V. |
