A data output circuit of a semiconductor memory apparatus includes a pre-driver generating pull-up and down signals from driving rising and falling data in active periods of rising and falling clocks, respectively, in accordance with a state of an output enable signal. A main driver generates last output data to a common node from the pull-up and down signals. An assistant pre-driver generates an assistant drive signal, which is activated when the rising data disagrees with the falling data, in correspondence with inputs of the rising data, the falling data, the rising clock, the falling clock, and a pipe output control signal. An assistant main driver generates assistant last output data to the common node from the pull-up and down signals in accordance with a state of the assistant drive signal.