A 40 Gbit/s driver, based on two cascaded double-distributed amplifiers has been designed and realised for driving lithium niobate modulator. The ICs were fabricated with the 0.15 µm gate length GaAs P-HEMT technology from Philips OMMIC. The driver module exhibits a state-of-the-art output driving voltage of 8 Vpp, in 50 ? load, and more than 26 dB gain over a 26 kHz to 43 GHz bandwidth.