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https://designers-guide.org/forum/YaBB.pl Design >> Mixed-Signal Design >> Settling of Diff AMP https://designers-guide.org/forum/YaBB.pl?num=1098118434 Message started by saber on Oct 18th, 2004, 9:53am |
Title: Settling of Diff AMP Post by saber on Oct 18th, 2004, 9:53am Hello, I have designed a folded-cascode differenctial amplifier used in the pipelined ADC. In settling simulation, I found that differential output (=vop-von) was well settled, but single-ended outputs (vop, von) were quite bad in waveform. I tried to make a good settling for single-ended output, but it was not so easy. Since differential output will be used in level-decision(comparators), could I ignore the single-ended result? |
Title: Re: Settling of Diff AMP Post by ywguo on Oct 19th, 2004, 6:39am Hi, Saber, Why do you require the single-ended outputs settling very well? Are those comparators differential or single ended? Thanks Yawei |
Title: Re: Settling of Diff AMP Post by John Galt on Oct 19th, 2004, 9:33pm Hi! Since your circuit is differential, I guess it doesn't make a difference whether the individual single-ended outputs settle properly or not as long as the differential output settles well and the output common mode voltage is within bounds. The next stage of the pipeline is sensitive only to the difference of the two outputs and their common mode, so as long as these two are accurate, you don't have a problem. |
Title: Re: Settling of Diff AMP Post by sheldon on Dec 19th, 2004, 6:36pm Hi, Have you checked your common-mode loop characteristics? For example, is the slew rate and the bandwidth of the common-mode loop faster than the differential mode? If the differential mode is faster than the common-mode loop. Then you could be have issues with the common- mode levels not settling well even though the differential mode characteristics look good. If this is the case, then you may want to modify the design so that the common-mode loop performance is sufficient for your application. Sheldon |
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