场效应晶体管(FET)是六十年代开始发展起来的单极性晶体管,与普通的双极晶体管相比,它的优点是:1.输入、输出阻抗都较高;2.动态范围大;3.具有平方律的传输特性;4.噪声系数低。此外还有温度稳定性高、抗辐射能力强、其电路更宜于集成化等。因此,在现代电子、通信、雷达、导航、抗干扰等各种技术设备中得到越来越广泛的应用。就无线电通信设备而 Field-effect transistors (FETs) are unipolar transistors that began to evolve in the 1960s. Compared with ordinary bipolar transistors, FETs have the following advantages: 1. High input and output impedances; 2. Large dynamic range; 3 Has a square law of transmission characteristics; 4 noise figure is low. In addition there are high temperature stability, strong anti-radiation ability, the circuit is more suitable for integration. Therefore, in modern electronics, communications, radar, navigation, anti-jamming and other technical equipment has been more and more widely used. On the radio communications equipment