The circuit in CMOS technology allows high speed driving of optical sources, in particular laser diodes, operating efficiently at speeds that meet the requirements imposed by optical fibre communication systems and avoiding interference between driving currents and biasing current in the optical source. The circuit comprises a bias current generator, a modulation current generator and a cascade of CMOS inverter stages that supplies a driving voltage to the modulation current generator and receives digital signals at its input. It is possible to independently adjust the bias current, so as to allow driving sources with different threshold currents, and to adjust the modulation current.