A 10 Gbit/s driver IC for lasers or lightwave modulators has been implemented using carbon-doped base AlGaAs/GaAs HBTs. The integrated circuit is intended for applications involving either direct or external modulation of laser sources. The circuit is capable of driving 60 mA into a 50Ω load with rise/fall times of 40 ps and generates a differential output voltage of 6 V peak to peak at 10 Gbit/s. Modifying the design slightly, a 9 V peak to peak differential output was achieved at 5 Gbit/s by switching 90 mA into a 50Ω load.