Gain bandwidth considerations in fully integrated distributed amplifiers implemented in silicon

A study of the gain and bandwidth limitations of a distributed amplifier implemented in silicon substrates is presented. It was found that the gain bandwidth product is limited to approximately 55% of the f_max of the gain stage used. This study considered three commonly used gain stages in a distributed amplifier: single device, cascode and Darlington f_T doubler. A limit on the bandwidth for the distributed amplifier is presented as a function of the choice of gain cell, quality of the passives, and the number of stages used. Gain and matching considerations are also presented. Measurements of three distributed amplifiers verify the simulation results.