I intend to design an audiometery system (the medical device). So far, I have ended with this idea to use PCM1792.
This device should produce signals which gain vary between 0 to 120dB.
There is an internal digital gain in PCM1792.
1) Can I use this feature in PCM1792 and get high-quality signals at 0 and 120dB?
2) How does the "dynamic range" changes when the gain volume is modified? In another word, can I get high quality signals both at 0 and 120dB when the gain changes from 0 to -120dB?
3) Is it better to cascade this DAC with a gain controller (such as PGA2311, ...) and control the gain by PGA, or do the gain control only with DAC?
4) How does the "dynamic range" of a DAC or a PGA varies with the selected internal gain. I have asked this question (for DAC only) in detailes here: http://e2e.ti.com/support/data_converters/audio_converters/f/64/t/171398.aspx#626270
Please see the post (http://e2e.ti.com/support/data_converters/audio_converters/f/64/t/171398.aspx#626270) for the impact of digital attenuation on dynamic range. For this application, it would make sense to use the PGA2311 because the attenuation is done in the analog domain even though it is digitally controlled. It has a DNR of 120dB itself, so it can ensure high quality signals.
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