Patent ID: 7339409

Claim:
An output driver for use in a semiconductor device, comprising: a pre-driving means for pre-driving a data signal in response to pre-driver bias signals; a main driving means for receiving an output signal of the pre-driving means to thereby drive an output pad in response to the output signal of the pre-driving means and the pre-driver bias signals; and a slew rate replica means for generating the pre-driver bias signals to constantly maintain effective resistances of a pull-up path and a pull-down path of the pre-driving means by modeling the pull-up path and the pull-down path of the pre-driving means, wherein the slew rate replica means includes: an external resistor coupled between a power supply voltage and a dummy pad; first comparing means for comparing a potential on the dummy output pad with a reference voltage to output a pre-driver pull-down bias signal; a first pre-driver pull-down replica coupled between the dummy output pad and a ground voltage for maintaining the potential on the dummy output pad at the level of the reference voltage in response to the pre-driver pull-down bias signal: a second pre-driver pull-down replica coupled between the ground voltage amd a first node, the second pre-drive pull-down replica having the same configuration as the first pre-driver pull-down replica; second comparing means for comparing a potential on the first node with the potential on the dummy output pad to output a pre-driver pull-up bias signal; and a pre-driver pull-up replica for maintaining the potential on the first node at the level of the reference voltage in response to the pre-driver pull-up bias signal.