A monolithic integrated transimpedance amplifier for the receiver in a 40-Gb/s optical-fiber TDM system has been fabricated in an InP-based HBT technology. Despite its high gain (transimpedance of 2 k/spl Omega/ in the limiting mode, 10 k/spl Omega/ in the linear mode) the complete amplifier was realized on a single chip. Clear output eye diagrams were measured up to 43 Gb/s under realistic driving conditions. The voltage swing of 0.6 V/sub pp/ at the differential 50 /spl Omega/ output does not change within the demanded input dynamic range of 6 dB. At the upper input current level even 48 Gb/s were achieved. The power consumption is approximately 600 mW at a single supply voltage of -5.5 V.