This is a simulation of the LM386 as Audio Amplifier: http://www.ti.com/lit/ds/symlink/lm386.pdf
Note: the 10 Ohms resistance on the right represents the speaker.
The AC voltage supply on the left side represents the output of a jack female connector of a smartphone (The one where you connect your headphones). The output signal has an amplitude smaller than 50mV which is amplified from 0 to 20 times (depending on the potentiometer) thanks to the LM386 operational amplifier.
