Data bus clamp circuit for a semiconductor memory device

Abstract

A data bus clamping circuit for use in a semiconductor memory device includes a memory cell array for storing data, a row address decoder for decoding row address signals taken in by a row address strobe signal to select memory cells in a row direction of the memory cell array, a column address decoder for decoding column address signals based on a column address decoder enabling signal to select memory cells in a column direction of the memory cell array, complementary data buses for transmitting data read out from the memory cell array, a data bus pull-up circuit for pulling up the complementary data buses, and a differential amplification type of readout circuit for amplifying on a differential basis data on the complementary data buses to output readout data. The data bus clamping circuit includes a first discharge circuit for discharging electric charge on the complementary data buses during an active period of the row address strobe signal, and a second discharge circuit for discharging electric charge on the complementary data buses with a discharge ability larger than the first discharge circuit, during a period of time from the time the active period of the row address strobe signal starts until the column address decoder enabling signal becomes active.