Polynomial Modeling and Parameter Estimation of Class B Power Amplifiers

Power Amplifiers are used in the output stages to provide sufficient power to an output load to drive a speaker or other power device, typically a few watts to tens of watts. Polynomial models can be used for power amplifier (PA) modeling. In this paper, a novel set of orthogonal polynomials are used for the modeling of a class B power amplifier by incorporating its nonlinearities caused due to crossover distortion. The coefficients of the polynomial are estimated using least squares method with the aid of observed input and output waveforms. The normalized mean square error (NMSE) is then calculated to understand the error between the observed and calculated output waveforms. The purpose of this model building is to have a thorough understanding of the integrated plant-controller circuitry involved in amplifier design. Further, this study would allow us to move towards reduction in distortion in the amplifier operation. We demonstrate our work using simulations on PSPICE.