# Filter circuit in Microphone [closed]

I am using VS1053 audio recording IC with a microphone.There, I found some filter circuit.How do they help the IC? https://www.sparkfun.com/datasheets/Components/SMD/vs1053.pdf

## closed as unclear what you're asking by Marcus Müller, Harry Svensson, Voltage Spike, winny, Lior BiliaNov 22 '17 at 16:15

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• "How do they help" is a very broad question. Do you understand what a filter does? Do you understand what digital audio recording does? Do you understand the sampling theorem? – Marcus Müller Nov 18 '17 at 13:49

Most of those capacitors aren't in filters that are intended to influence the frequency response of the microphone.

C17, C16 and R12A, R12B,R13A,R13B are there to provide a clean and stable DC voltage for the microphone from AVDDand AGND. Whatever circuitry uses the microphone signal has a differential input, and this arrangement powers the microphone in a way that is compatible with that requirement.

C13 reduces interference from RF (radio frequency) sources like cellphones.

C14 and C15 remove DC voltage from the signal so that the following amplifier with differential input doesn't have to deal with it. The sampling is done after the amplification inside the chip somewhere.

If C17 and friends weren't there, then every bit of electronic buzz and hum on AVDD and AGND would get into the microphone signal.

Without C13, you couldn't use the microphone near cellphones or other transmitters.

Without C14 and C15, the amplifier would probably just slap its output to one of the voltage rails and not be able to amplify the microphone signal - you wouldn't hear anything from the microphone.

The values chosen and the impedances (and resistances) around them are such that they should not influence the frequency response much at all. The smaller value capacitors should only have effects above the frequency range of the microphone, and the larger ones should all only have effect on frequencies too low to hear.