高频丙类功率放大器外文文献中英文翻译.DOC

毕业设计（论文）外文文献翻译 院 系：光电与通信工程系年级专业：09机电子信息工程姓 名：陈佳跃学 号：0906012149附 件：POWER AMPLIFIER   指导老师评语： 指导教师签名： 年 月 日 POWER AMPLIFIER  2.0  Introduction  The main characteristics of an amplifier are Linearity, efficiency, output power, and signal gain. In general, there is a trade off between these characteristics. For example, improving amplifier’s linearity will degrade its efficiency. Therefore knowing the importance degree of each one of these characteristics is an essential step in designing an Amplifier. This can be jugged based on the application. As an example high output power Amplifier is used in the transmitter side of a transceiver, whereas high linear amplifier used in the receiver side. An amplifier is said to be linear if it preserves the details of the signal waveform, that is to say, Vo (t ) = A · Vi (t )  (2.1) where, Vi and Vo are the input and output signals respectively, and A is a constant gain representing the amplifier gain. But if the relationship between Vi and Vo contains the higher power of Vi, then the amplifier produces nonlinear distortion. The amplifier’s efficiency is a measure of its ability to convert the dc power of the supply into the signal power delivered to the load. The definition of the efficiency can be represented in an equation form as  η=  Signal power delivered to load DC power Supplied to output circuit  .  (2.2)  4 5 For an ideal amplifier, the efficiency is one. Thus, the power delivered to the load is equal to the power taken from the DC supply. In this case, no power would be consumed in the amplifier. In reality, this is not possible, especially in high frequency realm of RF circuits. In many high frequency systems, the output stage and driver stage of an amplifier consumed power in the amplification process. The gain of the amplifier (G) is equal to the magnitude of the output signal (Xo) over the magnitude of the input signal (Xi) as shown in the equation.  G =  X o