| 摘要 |
PURPOSE:To obtain a power amplifier with high efficiency higher than 78.5% by varying the number of power amplifiers which are driven according to an output voltage by using >=2 linear power amplifiers, and supplying their composite output to a load. CONSTITUTION:Two class ''B'' power amplifiers 1 and 2, an analog switch 4, and a comparator 5 which supplies a switch signal to the analog switch 4 when an input signal level Vi exceeds a positive or negative reference voltage (+VTH1-VTH) are provided. The class ''B'' power amplifier 1 consists of power MOSFETs Q1-Q4 (having gates G1-G4) and an output transformer T1 and amplifies an input voltage Vi to an output voltage V1 (output current i1), and the class ''B'' power amplifier 2 consists of power MOSFETs Q5-Q8 (having gates G5-G8) and an output transformer T2 and amplifies an input voltage Vi' to an output voltage V2 (output current i2).
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