There are three development for the Middle Power Amplifier : the first stage power amplifier, the drive stage power amplifier and the last stage power amplifier .

本文对固态线性功率放大器的研制包括：前级放大器的研制、驱动级放大器的研制、末级放大器的研制。

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At last, we design an experimental system including signal source, power amplifier array and loudspeaker array. Some experiments of the directive property of loudspeaker array are completed.

最后，构建了一实验系统，该系统由信号源、功放阵列和扬声器阵列组成，并在实验室环境下完成了线阵列扬声器组的指向性实验和测试。

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"Last year,one of our staff members actually brought his own guitar and amplifier and led us in several rounds of song, Christmas songs and holiday songs.

VOA: special.2010.12.20