Sense amplifier and data reading method for memory

PURPOSE: To shorten an access time and to extremely reduce the consumption of electricity by opening by a suitable frequency a first and second switching means during reading operation and operating a low gain type of a first stage and a high gain type of a second stage so as to continuously amplify data stored in a selected memory cell. CONSTITUTION: Data switch control signals are induced from bit switch control signals, the operation of the first stage 16 and the second stage 17 are made to be successively performed, and a differential voltage between bit lines is made to be successively amplified. The second stage 17 is operated as not only a high gain amplifier but also a buffer. A data output node is connected to an output driver, and data output signals DO are obtained in its output. Also, a restoring and equalizing means are provided in the first stage 16 and the second stage 17, and the potential of a first data line, a second data line and the data output node are risen to a high potential VH during a restoring time period. By this way, the access time is shorten and the consumption of electricity is reduced. COPYRIGHT: (C)1990,JPO