A Novel Method to Determine Transistor Geometry for PA Design

Abstract

This method uses a new concept “Gain Number ${\left( {GN} \right)}$” and “Transition Frequency ${\left( {f_{Tr}} \right)}$” (between Maximum Stable Gain ${\left( {MSG} \right)}$ and Maximum Available Gain $\left. {\left( {MAG} \right)} \right)$ as figures-of-merit to select a most suitable HBT device for a PA design of a certain required frequency ${\left( {f \_ dsn} \right)}$. The key is to establish relationships between ${GN}$ and ${f_Tr}$, and the HBT's geometrical parameters and associated mathematical quantities: the ratio of an HBT's base pedestal area $\left. {\left( {A_B} \right)} \right)$ to emitter area $\left. {\left( {A_E} \right)} \right)$ and the product of base resistance $\left. {\left( {R_B} \right)} \right)$ and ${A_E}$.