| 摘要 |
<p>PURPOSE:To always perform the accurate and stable operation by switching and selecting between a sense amplifier for high speed and a sense amplifier for low speed time and reading out plural mask ROMs. CONSTITUTION:Memory cells 52l to 52n forming a mask ROM array 52 are read through a sense amplifier 14 for high speed time of a high inversion potential inverter or a sense am-plifier 16 for low speed time of a low inversion potential inverter. Only one of the outputs of these inverters 14 and 16 is selected by a select signal SE impressed to AND gates 20 and 22 of a sense amplifier switching circuit 18. Thus, the sense amplifier 14 is used by switching at the time of normalcy like the high-speed operation or the low-temperature operation, and the sense amplifier 16 having a low sensitivity is used by switching at the time of the high-temperature low-speed operation, and the malfunction of sense amplifiers is prevented to always perform the accurate and stable operation.</p> |
