Basic considerations and topologies of switched-mode assisted linear power amplifiers

• Published in: IEEE transactions on industrial electronics (1982) Vol. 44; no. 1; pp. 116 - 123
• Main Authors: Ertl, H., Kolar, J.W., Zach, F.C.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.02.1997; Institute of Electrical and Electronics Engineers
• Subjects: Applied sciences; Delay; Electrical engineering. Electrical power engineering; Exact sciences and technology; Feedback loop; High power amplifiers; Master-slave; Power amplifiers; Power electronics, power supplies; Power harmonic filters; Power transistors; Switching frequency; Topology; Transient response; Frequency characteristic; D class; Feedback system; Electric scheme; Linear amplification; Topology; Power amplifier; Switching
• ISSN: 0278-0046; 1557-9948
• DOI: 10.1109/41.557506

This paper presents a combined power amplifier system consisting of a linear amplifier unit with a switched-mode (class D) current dumping stage arranged in parallel. With this topology, the fundamental drawback of conventional linear power amplifiers-the high loss-is avoided. Compared to a pure class D (switching) amplifier, the presented system needs no output filter to reduce the switching frequency harmonics. This filter (usually of multistage type) generally deteriorates the transient response of the system and impairs the feedback loop design. Furthermore, the low-frequency distortions of switching amplifiers caused by the interlock delay of their power transistors are avoided with the presented switched-mode assisted linear amplifier system. This can be considered as a master-slave system with a guiding linear amplifier and a supporting class D slave unit. The paper describes the operating principle of the system, analyzes the fundamental relationships for the circuit design, and presents simulation results. Finally, various further topologies of switched-mode assisted linear amplifiers are given.