A Non-Closed-Form Mathematical Model for Uniform and Non-Uniform Distributed Amplifiers

A non-closed-form general mathematical model for CMOS distributed amplifier (DA) for broadband applications is presented. Contrary to the artificial transmission line (TL) assumption made in the conventional analytical models, the proposed model treats the DA as a discrete set of cells connected together, and hence considers propagation and mismatch between inter-cells. This approach provides designers with a much more accurate first sizing of the DA compared to conventional ways and, as a result, leads to a reduced design time and complexity. The model enables both quantitative and qualitative analysis of a DA, for the purpose of aiding the designers in predicting the relations between DA performance and its multi-design parameters, especially in the context of non-uniform designs. In addition, it is well suited to Computer-Automated Design (CAutoD), to help in achieving designs having a given set of performance goals. The validation of the model is demonstrated on two designs, by a comparison with simulations done in Keysight's ADS tool and using STMicroelectronics' 55-nm SiGe BiCMOS design kit. First design is inspired from an already published non-uniform DA design while second one proposes a 100-GHz bandwidth CMOS uniform DA with 8 dB of power gain, after using it in a CAutoD process.