Analysis of Hybrid Parameters of a Single Stage Small Signal Transistor Amplifier Using Two-Port Network

Abstract

This paper presents the analysis of the h-parameter of a single stage small signal transistor amplifier using two-port network. This is motivated by the need to have the rudimentary knowledge of the h-parameter transistor analysis model and to demonstrate its equivalence in the three configuration of the transistor. In this analysis, it was borne in mind the characteristics of a small signal operating conditions of the transistor. Among these characteristics is the assumption that Small – signal operations applies when variations are restricted to such a small amplitude that the partial differential derivatives can be applied. In the methodology, the transistor two-port network was used in deriving the hybrid parameter performance quantities from the first principle by applying partial derivative mathematical tool. The four variables of the input and output of the two-port network namely the currents and voltages which could be combined in six different ways were identified. These were described and analyzed by mathematical functions which relates one of the four variables to two other variables at a time, and by this, six various functions were generated. The partial derivatives of these functions were obtained and these gave the performance quantities which are the key components of the h parameter equations. The initial conditions of each of the component parameters where properly observed and substituted appropriately. This was then transformed into the equivalent circuits of the three transistor configurations. Since the transistor is frequently used for the amplification of sinusoidal currents, the changes in instantaneous total voltage and current were then replaced by root mean square ac quantities, which are considered to be impressed on the direct value. The results obtained are the basic h-parameter equations and the key components of the h parameter transistor model namely the Input Resistance, the Reverse Voltage Gain, the Forward Current Gain and the Output Admittance.