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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
- Labels:
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ispn:40238:1:0
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l1:314:1:0
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PSoC5LP
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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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I'm also interested in connecting a microphone to a PSoC5. Is there a cookbook recipe for this task?
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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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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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Hi,
what bias are you using before the PGA? What DC bias does the mic output have?
Thanks.
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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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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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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.