最近,外刊上报导了两种新的混合型微波放大器,现将有关这方面的报导,加以综合介绍如下: 1.混合型场效应——双极晶体管放大器这种放大器兼有场效应晶体管低噪声和双极晶体管高增益的优点。通常放大器由几级构成,第一级用砷化镓微波场效应晶体管放大器,作为前置放大器,获得最低的噪声系数。而其余几级用双极晶体管放大器,在最佳的匹配条件下,获得足够高的增益。比如,由飞歌—福特公司设计的一个混合型放大器就是采用这种技术,其工作在3.7～4.2 Recently, two new hybrid microwave amplifiers have been reported in the foreign media. The reports on this issue are summarized as follows: 1. Mixed Field Effect - Bipolar Transistor Amplifier This amplifier has both low field effect transistors The advantages of high gain of noise and bipolar transistors. The amplifier is usually composed of several stages, the first stage with GaAs microwave field-effect transistor amplifier, as a preamplifier, to obtain the lowest noise figure. The remaining few stages use bipolar transistor amplifiers to achieve sufficiently high gain under optimal matching conditions. For example, a hybrid amplifier designed by Philco Ford made use of this technology and operates at 3.7 to 4.2