US Patent 7554877 Apparatus and method for data outputting

An data output circuit for outputting a data stored in a core of a semiconductor memory device includes a clock generator for generating a rising clock and a falling clock by using an external clock, a clock repeater for outputting the rising clock and the falling clock as one of a high voltage clock and a low voltage clock in response to an external voltage level check signal, a level shifter for outputting a high voltage data generated by shifting the data synchronized with the high voltage clock, a data carrier for outputting a low voltage data synchronized with the low voltage clock, and a data repeater for outputting one of the high voltage data and the low voltage data in response to the external voltage level check signal.