# Designing a circuit with a LM386 amplifier

I'm designing a circuit an I want to use the LM386 audio amplifier. Before designing, I'm going through the whole datasheet, I've seen that VI is from -0.4V to 0.4V :

Here is the first typical application :

I'm just wondering if Vin is what they call VI just before ? Or is it a different value that will be higher since it will be divided by the potentiometer ? I don't find the datasheet very clear about that.

• VI is the voltage at the actual pins (2 and 3) of the LM386. Sep 29 at 14:31
• Keep in mind that minimum gain is 20. If the pot is wound all the way to the top, an input $V_{in}$ with peak amplitude greater than 0.4V will certainly cause distortion at amplifier output (and likely will distort with even lower $V_{in}$ ) Sep 29 at 14:49
• Bibibou: I'd suggest no more than 0.3V peak at input. Your question's schematic doesn't show gain...be aware that adding a capacitor in the feedback path (between pin 1 and pin 8) can increase gain from 20 up to 200. In that case, your input peak amplitude shouldn't exceed 0.003 V if you expect output to remain undistorted. Vcc also has an influence on the amplitude where distortion begins. Sep 29 at 15:21
• You said you have an audio signal that comes from an ADC. An ADC is used to convert an analog voltage to a digital value - you don't want to feed that digital value into an LM386 as the LM386 wants an ananlog audio signal as input. Sep 29 at 15:31
• The LM386 works well driving an 8 ohms speaker when its supply is 6V or 9V. When a 12V supply is used then its output is distorted and it heats a lot when driving an 8 ohms speaker but it can drive a 16 ohms speaker with up to 0.5W into the speaker and with 0.5W of heating. Sep 29 at 17:50

## 1 Answer

What comes out of the potentometer is less that what goes into the potentiometer.

The datasheet talks about inputs and pins of the IC, not any volume control or other circuitry that is connected to it.

Please understand that +/- 0.4V or 0.8 Vpp is the recommended maximum. It will usually be much less, as there is no way the chip can amplify such large input signal without clipping.