为了实现可变增益放大器高精度及大动态范围的优势，基于GaAs 0.25 μm pHEMT工艺，设计了一款工作在0.1~4.0 GHz并行控制的可变增益放大器。放大器由数控衰减器和射频放大器组成。数控衰减单元采用桥T型结构和电平转换电路来实现；正压控制衰减电路简化了电路结构，提高电路可靠性；改进型并联电容补偿衰减结构改善大衰减态高频衰减精度；射频放大器电路采用并联电阻负反馈的共源共栅（Cascode）结构，实现了高增益平坦度和大动态范围。测试结果显示，在工作频带内，可变增益放大器的增益可达20 dB以上、平坦度在1.5 dB以内，可变增益范围为0~31.5 dB、衰减步进0.5 dB，输出三阶交调点最高可达39 dBm，端口回波损耗均小于-15 dB。

In order to achieve the advantages of high precision and large dynamic range of variable gain amplifier， a high precision variable gain amplifier with parallel control operating in 0.1-4.0 GHz was designed based on a 0.25 μm GaAs pHEMT process in this paper. The variable gain amplifier consisted of a digital attenuator and a RF amplifier. Bridge T-shape structure and level conversion circuit were used to achieve digital attenuation unit. Positive voltage control circuit was adopted to simplify the attenuator circuit and improve the reliability of the circuit. Improved parallel capacitor compensation attenuation structure was introduced to optimize the high frequency attenuation accuracy of large attenuation state. The RF amplifier adopted common-source-common-gate （Cascode） structure with parallel resistance negative feedback， which achieves good gain flatness and large dynamic range. The measurement results show that from 0.1 GHz to 4.0 GHz frequency band， the gain is more than 20 dB， and the gain flatness within 1.5 dB. The attenuation step is 0.5 dB， the variable gain range is 0-31.5 dB， the output third order crossover point can reach up to 39 dBm and the port return loss is less than -15 dB.