Transmission apparatus for differential communication

A transmission apparatus for differential communication comprising:

• a driver bridge circuit including a first output device connected between a power line, supplied with a power-supply voltage from a direct current power supply, and a first transmission line, a second output device connected between the first transmission line and a ground line, a third output device connected between the power line and a second transmission line, and a fourth output device connected between the second transmission line and the ground line, the first and fourth output devices being paired to form a first output device pair, the second and third output devices being paired to from a second output device pair, the first and second output device pairs being alternately tuned ON and OFF in accordance with transmission data to perform differential transmission of the transmission data through the first and second transmission lines;
• and
• a noise reduction device configured to reduce noise superimposed on the first and second transmission lines, wherein
• the noise reduction device includes a pair of noise protection circuits, each noise protection circuit being provided to a corresponding one of the first and second transmission lines,
• each noise protection circuit includes a ground potential detector and an impedance controller,
• the ground potential detector detects a potential of the corresponding transmission line with respect to the ground line, and
• the impedance controller causes an impedance of the corresponding transmission line with respect to the ground line to become equal to an impedance of the other transmission line with respect to the ground line, when the detected potential becomes outside a predetermined potential range of from a lower potential limit to an upper potential limit that are set based on the power-supply voltage.