Projeto e avaliação de desempenho de um amplificador de áudio sem realimentação negativa global utilizando transistores bipolares de junção

Abstract

This work proposes the development of an audio amplifier without global feedback using bipolar transistors of junction. It will be used as the basis of the article “A design methodology for audio amplifiers without global negative feedback: proposal and validation” Visintin et al. (2022) in order to perform a comparison between amplifier approaches using transistors field effect and bipolar junction transistors. The present study aimed to develop a circuit class AB audio amplifier, with 50Wrms at 8Ω for this, three stages with bipolar transistors of junction operating with symmetrical voltage of ±90V and in the voltage gain stages and ±45V in the output stage. The practical results satisfied the design requirements, such as: Slew Rate above 3.6V/μs (53.77V/μs), cutoff frequency higher above 40kHz (342kHz), Total Harmonic Distortion below 0.5% (0.0978% average at 50W). Also, to ensure that the amplifier projected presents a good linearity, the intermodulation distortion in 50W (-46.08 dB) was measured. In this way, the effectiveness of the proposed method for the design of audio amplifiers without global negative feedback using bipolar transistors of junction.