Patent ID: 7260057

Claim:
A data transmission system comprising: a first semiconductor integrated circuit provided with an external terminal and a data signal output circuit connected to the external terminal; a second semiconductor integrated circuit provided with an external terminal and a data signal input circuit connected to the external terminal; and a transmission line, connected to the external terminals, which transmits a data signal from the first semiconductor integrated circuit to the second semiconductor integrated circuit, wherein the data signal input circuit has two or more differential amplifiers that compare signals inputted to data input terminals with reference voltages to discriminate the inputted signals, and wherein one of the differential amplifiers to which the highest reference voltage is applied is a first type differential amplifier of which input differential transistors have n-channel field effect transistors, the other of the differential amplifiers to which the lowest reference voltage is applied is a second type differential amplifier of which input differential transistors have p-channel field effect transistors, and these differential amplifiers discriminate three levels or more of the transmission line to thereby discriminate reception data.