Patent ID: 7667531

Claim:
A signal transmission circuit including two or more prescribed number of lanes, comprising: a constant voltage circuit to generate a constant voltage; a current supply circuit to receive the constant voltage from the constant voltage circuit, and generate and output in parallel the prescribed number of currents having a value corresponding to a prescribed voltage-current conversion ratio; and a driver circuit placed for each lane to receive a current output from the current supply circuit and output a voltage having an amplitude corresponding to the prescribed voltage-current conversion ratio, wherein the current supply circuit includes: a current supply control circuit capable of changing the prescribed voltage-current conversion ratio; a constant current generation unit to generate a constant current having a value corresponding to an input voltage; and a constant current output unit including the prescribed number of output terminals to output the constant current generated in the constant current generation unit from each output terminal to a corresponding driver circuit, and the current supply control circuit comprises: a voltage divider circuit to divide the constant voltage from the constant voltage circuit and obtain a plurality of output voltages; and a selector to select one from the constant voltage and the plurality of output voltages and output the selected one to the constant current generation unit.