STUDY OF TOPOLOGIES FOR AMPLIFIERS WITHOUT GLOBAL FEEDBACK

• Grant number: 25/20617-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: December 01, 2025
• End date: November 30, 2026
• Field of knowledge: Engineering - Electrical Engineering - Electrical, Magnetic and Electronic Circuits
• Principal Investigator: Carlos Alberto de Francisco
• Grantee: Carlos Eduardo Lopes Scotti Falcuci
• Host Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil

Abstract

The pursuit of high-fidelity sound reproduction has driven decades of research and innovation in audio amplifier design. One of the most widely adopted techniques in this field is global negative feedback, which provides significant improvements in key performance parameters such as harmonic distortion reduction, enhanced stability, and extended frequency response. However, this approach has also faced criticism within both the audiophile and technical communities. Reports suggest that excessive feedback may introduce undesirable artifacts, such as high-order harmonics and timbre alterations, ultimately compromising the naturalness of the reproduced sound. This research project aims to investigate and consolidate audio amplifier topologies that operate without global negative feedback. The absence of this technique demands a more rigorous design process to ensure stability, linearity, and gain control through alternative means, including careful selection of amplifier stages, precision components, and strict bias point management. Performance parameters such as slew rate, total harmonic distortion (THD), and frequency response will be targeted to maintain signal quality and fidelity. The selected amplifier topologies will first be simulated using LTspice, enabling detailed analysis and optimization regarding current consumption, gain, and bandwidth. Subsequently, individual amplifier stages will be prototyped and tested experimentally to validate the simulation results. This methodology will provide insight into the practical challenges and advantages of feedback-free amplifier design, offering technically viable alternatives for high-fidelity applications. (AU)