How to sample a microphone with best signal to noise ratio?

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Anonymous
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Hi,

   

I am trying to preamplify and sample a microphone signal, but I get a lot of noise.

   

The microphone gives a maximum of about 3mV of signal amplitude. So at the moment I use a single inverting PGA with gain 49 and try to use lowest possible range +/- 256mV of the 16-bit Sigma Delta ADC omitting it's input buffer. The signal to noise ratio of this setup seems to be only about 6 bits.

   

What is the best method using the internal amplifiers?

   

Many thanks!

   

Christof

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8 Replies
Anonymous
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cebersp,

   

 

   

Can you please let us know how you were able to arrive at the figure of 6-bits for signal to noise ratio?

   

Are you using a condenser mic for the project?

   

 

   

Regards,

   

dasg

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Anonymous
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 I'm also interested in connecting a microphone to a PSoC5. Is there a cookbook recipe for this task?

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Anonymous
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You should try to send the output of your PGA to a pin and see if the noise is from the PGA or your input. I would prefer to use the op-amp if lower noise is needed.

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Anonymous
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The best gains are provided in the ADC itself. There is the buffer that can also provide you the gain.

   

With buffer gain set to 8 and ADC range set to provide a gain of 16 you can achieve an effective gain of 128.

   


 

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Anonymous
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Hi,

   

   what bias are you using before the PGA? What DC bias does the mic output have?

   

Thanks.

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NidhinM_71
Employee
Employee
25 solutions authored 10 solutions authored Welcome!

Here is the microphone circuit

   

   

 

   

Design the values of R_1,R_2 and C_1 based on mic specifications and Vdd value. You may try connecting another capacitor across R_2 to reduce noise or to fine tune the response.

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Anonymous
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Since the ADC is best utilized in its digital config maybe making that resistor network with 3 resistors and gettting a differential input might help. Just a thought.

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Anonymous
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Since the ADC is best utilized in its differential config maybe making that resistor network with 3 resistors and gettting a differential input might help. Just a thought.

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