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https://designers-guide.org/forum/YaBB.pl Design >> Analog Design >> how 2 reduce the systematic offset of a folded cascod comparator https://designers-guide.org/forum/YaBB.pl?num=1239145764 Message started by Tofu on Apr 7th, 2009, 4:09pm |
Title: how 2 reduce the systematic offset of a folded cascod comparator Post by Tofu on Apr 7th, 2009, 4:09pm Hi: I made a comparator based on folded cascode structure due to headroom issue. It's systematic offset is in the range of 3mv which is a bit large than the spec (<900uv). I wonder if there is any knobs (e.g., current, diff pair, load, etc) for this type of architecture that I can tune to decrease the number? and how? thanks a lot! |
Title: Re: how 2 reduce the systematic offset of a folded cascod comparator Post by wave on Apr 7th, 2009, 5:52pm Sounds like your folded legs may not match. Check their currents, Vds, and Early effects. ;D Wave |
Title: Re: how 2 reduce the systematic offset of a folded cascod comparator Post by raja.cedt on Apr 8th, 2009, 12:49am have you got expected output common mode voltage?and check common mode at two outputs,if they are not symmetric..as he said its like current mismatch problem,.And if possible decrease the overdrive voltage of differential pair..it may help Thanks, rajasekhar. |
Title: Re: how 2 reduce the systematic offset of a folded cascod comparator Post by loose-electron on Apr 17th, 2009, 10:50pm Offset is almost always dominated by the mismatch of the differential pair at the input. You should consider an architecture that has minimal systematic offsets and then uses a method of offset cancellation to deal with mismatch issues. |
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