Output noise of PGA2310 or PGA2311 or PGA4311 (for dynamic range) - diyAudio
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Old 25th January 2012, 11:34 PM   #1
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Default Output noise of PGA2310 or PGA2311 or PGA4311 (for dynamic range)

Hi
Example is given for PGA4311:
When the gain of the IC is set to 0dB and its input is grounded, a 2.5uVrms noise is produced at the output.
If the gain of the IC is reduced (for instance, -60dB) do we expect a lower Vrms for the output noise, or the output noise is mostly a function of Vcc?
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Old 26th January 2012, 09:50 AM   #2
sesebe is offline sesebe  Romania
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Location: Iasi
Default How you measure this noise?

I like to speak only about measurable things.
If you can measure this noise level then you can make another measurement with other gain setings.

At this noise level anythig can increase the noise but to lower it is very questionables.
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Old 26th January 2012, 10:42 AM   #3
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Default More description about my uqestion

Let me ask my question in another way. I want to feed the PGA with a normalized-amplitude audio signal (I can determine the normalization factor) and control the gain of the audio signal by gain programming the PGA.
Suppose that the normalization factor is set to 0.0420Vrms. At this voltage if the PGA gain is set to +35.5, the output signal has the maximum allowed Vrms (here 2.5 V).
Vnorm = 2.5 * 10^(-35.5/20) = 0.0420 Vrms
Now if I change the PGA gain to -91.5dB, the output voltage for this normalized input value is:
Vout = 0.0420 * 10^(-91.5/20) = 1.117 micro Vrms
which is less than the indicated rms voltage of the output noise at 0dB gain (2.5 micro volt given in datasheet).
Now I want to know, does this noise decreases by the decrease of PGA gain (when the PGA gain changes from 0 to -91.5) or not?
Thanks
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