Low Noise High Stability Amplifiers over Very High Frequency Range Using Mismatching Approach within Linvill Plane Simulation

Abstract

A software approach was utilized to study the gain stability over a long frequency range in the order of 10 decades. The approach addresses the input and output power representations on the Linvill plane over a given frequency range. The study considers the mismatching approach by adding input and output admittances to keep the transducer gain of the system stable with a high stern stability factor. The study was extended to cover optimum noise figure over a frequency range of 10Hz-100GHz. The new selection technique uses a MATLAB script to calculate the Y parameters of a common emitter BJT amplifier for a wide frequency band. From the Y parameters, calculations for the optimum shunt admittances for the source and load are made based on a customizable threshold for the Stern stability factor. Additional calculations are made to optimize the source conductance to achieve the lowest noise figure. The program then calculates the noise figure at optimum stability and the stability factor at optimum noise. Initially, the device was instable for 2 decades within the MHz range, and after applying the described approach, the device was stable for the entire 10Hz100GHz frequency range. The transducer gain of the stabilized device was lower than that of the initial instable device.