A monolithic 5 to 45 GHz distributed amplifier has been developed utilising 0.25 μm InAlAs/InGaAs lattice matched cascode HEMTs with a mushroom gate profile as active devices. A measured gain as high as 15±1 dB from 5 to 40 GHz and a measured noise figure of 2.5–4 dB in the Ka-band were achieved.