在检拾接收信号幅度起伏较大的应用场合,一般均需使用自动增益控制电路。左图是使用一个结型场效应管来实现自动增益的简单电路。它的工作原理是通过改变Q_1的栅—源极间电压来直接改变它的漏 Pick up and pick up the signal amplitude fluctuations in the larger applications, generally require the use of automatic gain control circuit. The picture on the left shows a simple circuit that uses a junction FET for automatic gain. It works by changing the gate-source voltage of Q_1 to directly change its drain