Patent ID: 7378877
Filing Date: 2008-05-27
Classification: H04L

Abstract:
1. An output buffer including a pre-emphasis function for delivering a logic signal to a transmission line operating as a distributed constant circuit, comprising: a first buffer for receiving as an input thereto a first signal assigning a logical value to a logic signal and thereby driving the transmission line; a second buffer for receiving as an input thereto a second signal having a predetermined logical relationship with the first signal and thereby driving the transmission line in cooperation with the first buffer; output delay means for delaying an output signal from the first buffer for a predetermined period of time and an output signal from the second buffer for a predetermined period of time; and means for detecting a change in the logical value of the logic signal, wherein: output impedance of the second buffer is set to be higher than output impedance of the first buffer on condition that attenuation of a signal through the transmission line is reduced; and if a de-emphasis state continues, the second buffer operates in cooperation with the first buffer to drive the transmission line.