АРУ
Зеленый - выход, красный - уровень, до которого будем усиливать, рыжий - считает амплитуду выходного сигнала
Green line is the output, red line - to this level we will amplify input signal (sinus in the left part), orange - calculates an amplitude of output signal.
You can change amplitude of input signal within 100-400mV (we create this for microphone) and circuit will adjust this voltage to what you have in red line
You should wait a little for circuit stabilization