Increasing Gain of SPH8878LR5H-1 MEMS Microphone Breakout Board

Sensors Sound & Audio
1

Hi Sparkfun Community,

I am using the Analog MEMS Microphone Breakout Board (SPH8878LR5H-1) for audio input into a line level recorder. Unless the sound is coming very close to the mic it is too quiet.

Does anyone know if there is a way to increase the gain on the Op Amp Circuit? Looks like I would have to swap out an SMD component to do so, any advice or pointers? I like the quality of the audio but just need to be able to pickup quieter sounds too.

Thanks in advance for any guidance!

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2

To increase the gain, increase the ratio R4/R3. R4 = 300K for x64, R4 = 1Meg for x213.

You may run into oscillation or stability problems if you increase the gain too much, as the gain-bandwidth product of the OPA344 is only 1 MHz.

3 Likes
3

Awesome, thank you! So I should be able to just replace R4 with say a 500K (ie. 504 code SMD) and it should increase the gain a bit?

4

500/4.7 = x106

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5

How can i reduce the gain to 0?
Will removing one of the resistors work?
Is there any issue with no gain ?
My motherboard already have an opamp

6

In that case, use a gain of 1, not 0. Replace the feedback resistor with 4.7K.

Hint: gain = (output voltage)/(input voltage)

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