| 摘要 |
A transformer 11, which converts input current into voltage output, is arranged between a power switch 1, which amplifies and outputs audio signals based on the power source voltage VDD supplied to MOS transistors Q1 to Q4, and a speaker 3. Through appropriately determining the turns ratio (Ns/Np), without causing the power source voltage VDD of the power switch 1 to be large, large voltage Vs is made to occur at both ends of the speaker 3 from such small power source voltage VDD. Through this, large output power can be obtained.
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