Anto Besline
New Member
I have LM386 audio amplifier IC to make a simple audio amplifier. but i was get confused on selecting the capacitor to reduce noise.. any one can help me..
How to make a simple audio amplifier
- Thread starter Anto Besline
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Capacitor to reduce noise? Are you talking about the power supply bypass capacitor?
Here's the Texas Instruments data sheet: http://www.ti.com/lit/ds/symlink/lm386.pdf
Tell us which bit is confusing you.
Here's the Texas Instruments data sheet: http://www.ti.com/lit/ds/symlink/lm386.pdf
Tell us which bit is confusing you.
elnaldo
Lunatic Member
Usually, the circuit suggested by the datasheet is enough (page 8, 9 , 10 of the datasheet). When I fix some small amp using those ICs, the circuits match closely the IC datasheet
Here is a page designing an amp and explaining each capacitor used: http://www.circuitbasics.com/build-a-great-sounding-audio-amplifier-with-bass-boost-from-the-lm386/
Here is a page designing an amp and explaining each capacitor used: http://www.circuitbasics.com/build-a-great-sounding-audio-amplifier-with-bass-boost-from-the-lm386/
Anto Besline
New Member
thank you so much.. my problem have been solved... thankyou 100 times..
Retrovert
Addicted Member
The decoupling capacitor on the LM386 is normally used to prevent power supply noise from being amplified. The input stage is high-gain and will happily amplify supply ripple and noise. A battery supply can eliminate the need for the bypass capacitor.
If any sort of wall wart is being used as the power supply, or one of the noisy three-terminal regulators is used, decoupling at pin 7 is required. The amplifier will be quite noisy and buzz without it.
Omission of the capacitor when using an AC-DC supply, instead of a battery, is a common mistake made by hobbyists in the designs posted on the internet.
Note that batteries, particularly alkaline ones, have high internal impedance and thus cannot rapidly respond to changing current demands. The solution is decoupling the battery using a capacitor.
Yeah, not so much. That circuit is not compliant with the datasheet's sample design.
Off the top of my head...
The design has omitted the capacitor across the gain pins, which limits the gain to the setting of the internal resistor which is 20, instead of the maximum of 200. That may be fine for the intended application, of course.
The design lacks feedback which increases distortion. The datasheet spells this out.
The input is missing a blocking capacitor to eliminate DC from the input signal and avoid disturbing the LM386's internal biasing.
As per the above description, it's missing the bypass capacitor which may or may not be needed, but it's a good idea for any portable audio which can be powered from a wall wart.
The 1,000 µF DC blocking capacitor at the output is excessive and needlessly expensive. 220 µF would be perfectly fine and a lot less expensive, particularly for stereo where two are required.
Not good design at all. I would NOT use this circuit.
The TI circuit posted by rothwellaudio is the right place to start. Anything else is likely to be broken because hobbyists tend to have a very poor understanding of why manufacturer datasheets specify certain configurations.
