Linear Power Amplifiers: Basic Considerations of Switched-Mode Assisted Amplifiers
The paper presents a combined high efficient amplifier system consisting of a linear amplifier unit with a switched-mode(class D) current and voltage 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 cascaded type) generally try to avoide the transient response of the system and impairs the feedback loop design. Furthermore, the low-frequency distortions of switching amplifiers caused by the inter system response delay of the power transistors is avoided with the presented switched-mode assisted linear amplifier system. This consideration as a master-slave system with a guiding linear amplifier and a supporting class D slave unit. The work describes the operating principle of the system, analyzes the fundamental relationships for the circuit design and presents simulation results with the help of virtual lab. Keywords - class D, harmonics, transient error, etc