A MATHEMATICAL-MODEL OF A FIELD-EFFECT TRANSISTOR POWER-AMPLIFIER

In the course of development and investigation of SW linear power amplifiers (PA) (for amplifying SSB signals), the need arises to evaluate qualitatively and quantitatively their electrical parameters, such as P(u), the useful output power, R(e), the equivalent load resistance, efficiency, the coefficients of combined distortions of the third K3f and fifth K5f orders, transistor electrode voltage, etc. To determine these parameters, a mathematical model of an amplifier is used, which consists of a field-effect transistor model and the elements that comprise an amplifier. Several reports deal with transistor models [1-3]. In the models describe in [4-8], a number of substantive nonlinear elements are left out of consideration when determining the coefficients of combined distortions. The purpose of this paper is development of a mathematical model of a large-signal PA with allowance for the substantial effect of transistor non-linearities on the quality of its operation (C(zio), the input capacitance, C(zso), transfer capacitance, dependence of the sink current I(s) on voltages on the gate E(zi) and sink E(si)).