Mini Amplifier with LM386.

Source: http://www.josepino.com/?mini_amplifier_lm386   Tags: electronics circuits homemade audio

This is one of my favorites. The LM386 is a low voltage audio power amplifier. It can provide 125mW to 750mW, enough for any project that uses audio. This circuit can work with batteries, requieres minimum external parts and works from 4 to 18 Volts (contact the manufacturer or read the technical info. Some versions works only with 5 to 15V.)

The power output depends of the voltage. The power output is 125mW when the voltage is 6V. The voltage gain goes from 20 to 200 and the output is self-centering, so doesn't need dual voltage as other amplifiers. It can be used on battery radios, tape players, intercoms, also, as ultrasonic amplifier. This chip is the "555" of the amplifiers.
Taken from http://www.josepino.com
Here is the typical application for this chip. Here are two schematics, the first one have a gain of 200 and the second one is only 20. You can use a switch for the 10uF capacitor to have the "boost" option.

The 10k resistor is used to adjust the sensibility if the electret microphone, the 100k resistor is used to adjust the volume.

In theory, this circuit will not work because it needs a pre-amplifier. Supposedly, a 741 or any othe pre-amplifier is needed. As I said before, I don't follow the theory. I already verified that the pre-amplifier is not needed, just adjust the 10k variable resistor. In fact, You may not be able to get the circuit to work properly with a pre-amplifier.

Warning: May be too loud

The 220uF capacitor can be replaced by any other if that value is not available. Do not connect the speaker directly to the output pin. If you are using a tweeter (or piezoelectric) you can connect it directly.

7/9/2006 - UPDATE: This schematic can be used for almost ANY application that needs an amplifier. The switch labeled "Boost" activates the gain of 200 if the input signal is too weak.

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08/22/09 - 13:55:28 WILLIAM BERBARI from Brasil BH wrote: Circuito simples e funcional.Montado em SMD pode ser embutido em qualquer Ipode.
10/19/09 - 03:02:45 Clement from Malaysia wrote: Is your circuit work with any mic, other than the electret mic? How abt the PC mic or other professional mic?
10/19/09 - 03:06:01 José Pino wrote: I didn't try it with any kind of microphone but it should work with any kind of microphone.  In that case, the value of the 10k resistor should be changed or removed.
10/22/09 - 02:19:22 Joe from Cumming, GA wrote: It appears that the page below is supposed to have 2 schematics, but there are none. I have looked at some of your other pages, and the diagrams come up okay. Thanks.
http://www.josepino.com/?mini_amplifier_lm386
10/22/09 - 02:42:58 Joe from Cumming, GA wrote: This concerns my earlier comment. I am using Firefox, and I had it set to display pages with black text on a white background. With this, I couldn't see these schematics. I changed the setting to use colors as directed by the site, and now I can see the circuit diagrams. I don't know why the earlier setting caused a problem, but apparently it did.
10/22/09 - 02:56:41 Joe from Cumming, GA wrote: When I first sent this msg, the site told me that a similar msg had been posted. That was my msg, and this is an update.
I am using Firefox, and I had it set to display pages with black text on a white background. With this, I couldn't see these schematics. I changed the setting to use colors as directed by the site, and now I can see the circuit diagrams. I don't know why the earlier setting caused a problem, but apparently it did. - I now have a new problme. Although I can now see the schematics, they won't print, altho the text will. How can I print the schematics?
10/22/09 - 03:04:38 José Pino wrote: Sorry for the inconvenience Joe. The problem is the GIF image.  It was set to be a TRANSPARENT GIF, so any other setup or configuration color in the background will show only a dark image.  I can't fix it right now, but I will take care of the issue.  I'm afraid that images cannot be printed.
10/29/09 - 04:26:12 gus from new york wrote: meanwhile, i'd like to do this too, but have no idea where to begin :) help please?

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