In this blog, we have to make an audio amplifier using LM386 and study how to remove noise in an audio amplifier. It's very simple and cheap.
All this circuitry we have to make on a small mini breadboard.
The circuit diagram or the connection of this setup is shown by using the sketch.
Firstly you need a 3.5mm audio jack and separate this jack from the headphones. Next, we need an LM386 IC.
It is so popular for audio amplification. This IC needs a minimum external connection port.
This IC also battery operated with a wide supply voltage range 4 to 12V or 8 to 16V depending on the different manufactures series.
Next moving to the circuitry,I am using the 9V battery but I recommend 12V power supply or a 12V nickel-cadmium battery for better performance.
Next, I recommend 0.1uf(104) disc type capacitor which is connected in parallel with pin no 6 to pin no 2 connected ground through pin no 2. Pin no 6 is +Vcc.
This disc type capacitor is connected parallel with the power supply for removing Bebber and protecting IC from the instant power supply.
The pin no 7 is bypass. This pin is connected to a 10uf capacitor which is used for filtering. In this 10 to 100 uf of the capacitor works well.
You have seen a lot of circuits on the internet but in our circuit some changes at the output of the amplifier. The pin no 5 is the output pin there is an RC high pass filter.
It passes (2MHz) high frequency to the ground, so it cannot interfere with the audio amplifier. So this RC high pass filter circuit is replaced with the only 0.1uf (104) disc type capacitor.
I found that this is the best solution and it works for all the speaker. And it also helps that the noise from power supply doesn't pass through the audio amplifier.
And also at the output of the LM386 IC. I use a 1000uf (25V) electrolytic capacitor or use higher than that for removing DC offset it means no dc voltage pass into the speaker which will damage so capacitor prevent it and provide a wide base speaker.
if you are connected disc type capacitor at the output pin its prevent from unwanted oscillation.