Patent ID: 7308209

Claim:
A transmitter circuit comprising a light source ( 20 ) and arranged to operate said light source ( 20 ) to transmit optical communication signals in response to electric input signals from a first ( 11 ) and a second ( 12 ) circuit point between which circuit points a balanced electric input signal is intended to be present, wherein said transmitter circuit comprises a first circuit branch ( 21 ) which extends from said first point ( 11 ) via a third point ( 13 ) to at least a fourth point ( 14 ) and wherein said transmitter circuit comprises a second circuit branch ( 22 ) which extends from said second point ( 12 ) via a fifth point ( 15 ) to at least a sixth point ( 16 ), wherein said light source ( 20 ) is connected between said third ( 13 ) and fifth ( 15 ) points, wherein the components which are positioned on said first ( 21 ) and second ( 22 ) circuit branches are chosen such that the transmitter circuit is formed with a symmetry which is such that under normal operation conditions a balanced drive voltage is the case between said third ( 13 ) and fifth ( 15 ) points, which balanced drive voltage only depends on the voltage difference between said first ( 11 ) and second ( 12 ) points, wherein also the modulation current though the light source ( 2 ) only depends on said voltage difference.