| 摘要 |
PURPOSE:To improve the integrated degree of a ROM by making the threshold voltage of a MOS transistor more than four types and applying the memory capacity of more than 2 bits by one transistor. CONSTITUTION:The threshold voltage of the MOS transistor 5 of a memory transistor is made more than four types of the voltages A-D and the transistor 5 is detected by three types of detecting circuits S1-S3 forming the differential amplifier of reference voltages ref1-ref3 corresponding to the respective thresholds A-D. Then, the detected outputs D1-D3 of the circuits S1-S3 indicate the values of a table I, when a logical processing is applied to combine more than two types of the outputs D1-D3, the capacity of more than two bits is applied to the one memory transistor. Consequently, the number of the memory transistors can be reduced and the integrated degree of the ROM can be improved. |
