EN-Genius Network's Dennis Feucht answers your design
queries in his new Circuit Design Clinic!
July, 2009
EN-Genius Network presents a new, interactive
analog design service to readers! Send us your design questions (with
relevant data; schematics in JPEG or GIF, please) for some free
engineering advice from EN-Genius Network's circuit
consultant, Dennis Feucht, on how you might solve a design problem or
improve circuit performance. Submissions may be edited for clarity or
brevity, and submitters and their email addresses will remain anonymous
(unless otherwise indicated). Please send your questions to Dennis here.
High-Efficiency Linear Amplifiers 2 by Dennis L Feucht
In the December 2006 “Dear Dennis” column, we brainstormed ideas about how linear amplifiers might be made more efficient and perhaps preferred to switching amplifiers for applications requiring low noise as well. The basic idea was to segment the output into N parallel stages so that, like a bar-graph decoder, only one stage is on at a time over a limited output voltage range that is near the supply rail of that stage. With minimal voltage across the output transistor, power loss is minimized and efficiency increased. The scheme depends upon having a multi-voltage supply: this can be accomplished with different taps on the supply transformer secondary winding, whether it be switching or line-frequency. In either case, the efficiency remains largely unaffected by the multiple output voltages, one per output-stage segment.
