An InP/InGaAs HBT cascode amplifier operating from a single 5 V power supply is described. The circuit has a DC gain of 17.2 dB and a −3 dB frequency point of 12.3 GHz. This results in a gain-bandwidth product in excess of 90 GHz. The frequency response of the amplifier remains constant if the power supply voltage is as low as 4 V.