<div dir="ltr">Hi Tom,<br>I tried several schemes with 802 but unfortunately I did not reach a satisfactory result in DAC, considering that it is 16 bits. If it reached a noise ratio of around 12 ~ 13 bits, it would already suit my application. And the worst thing is that I have more than 100 parts in stock waiting for a solution to the problem. <div>I will test your suggestion, thanks.<br><div><br></div><div>Vinicius Brazil</div><div><a href="http://www.vbrazilsystems.com">www.vbrazilsystems.com</a></div></div></div><div id="DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2"><br> <table style="border-top:1px solid #d3d4de">
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<a href="#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2" width="1" height="1"></a></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, May 5, 2021 at 6:20 AM Tom Wiltshire <<a href="mailto:tom@electricdruid.net">tom@electricdruid.net</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div style="overflow-wrap: break-word;">Hi all,<div><br></div><div>The dsPIC 33FJ128GP802 uP (and others in the family) includes a 16-bit DAC on the chip. The outputs from the DAC are provided as a differential output to help cancel any noise generated by the uP internally. NOt a bad idea, seeing as that is probably inevitable. Despite this precaution, the DAC is reasonably noisy and not suitable for all applications.</div><div><br></div><div>The example circuit for combining the differential outputs is shown attached - a simple diff amp with 10K resistors everywhere.</div><div><br></div><div>Now, my question is this:</div><div><br></div><div>If I change the gain of the differential amp by increasing R6/R8 (to 47K, say) does this affect the noise cancellation properties of the diff amp?</div><div><br></div><div>It seems to me that it might, because the positive input now has a different proportion of signal going to it than the negative input.</div><div><br></div><div>Thanks,</div><div>Tom</div><div><br></div><div><div>
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