Highly-linear transimpedance amplifier for remote antenna units

In this paper, a highly-linear low-noise transimpedance amplifier (TIA) for use in the downlink receiver of remote antenna units in distributed antenna systems is presented. It is intended for intermediate frequency over fiber (IFoF) communications at 500 MHz. With the implementation of a programmable transimpedance, IFoF transmission is achieved, showing a very low error vector magnitude over a large optical input dynamic range. The topology consists of a fully-differential shunt-shunt feedback TIA, which has been designed and fabricated in a 65-nm RF CMOS technology with a 1.2-V voltage supply. A driver based on a cascode configuration has been implemented for measurement purposes. The total power consumption is 19 mW, from which the TIA dissipates 6 mW, while it achieves a bandwidth of 700 MHz.