Design optimisation of HBT broadband distributed amplifiers

Microwave simulation of heterojunction bipolar transistor (HBT) distributed amplifiers is carried out by separating the HBT equivalent circuit into base and collector transmission line circuits. The characteristics of the base and collector equivalent circuit are evaluated by analysing each individual device parameter. The optimal values of R/sub be/, R/sub bb/ and C/sub be/ have been obtained through the analysis. The relevance of feedback base collector capacitance (C/sub bc/) has also been considered in order to improve the gain-bandwidth product for an ultra broadband amplification.