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how 2 reduce the systematic offset of a folded cascod comparator (Read 3412 times)

Tofu

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how 2 reduce the systematic offset of a folded cascod comparator
Apr 07^th, 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!

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wave Senior Member Offline Posts: 117 Silicon Valley	Re: how 2 reduce the systematic offset of a folded cascod comparator Reply #1 - Apr 7^th, 2009, 5:52pm Sounds like your folded legs may not match. �Check their currents, Vds, and Early effects. Wave
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raja.cedt Senior Fellow Offline Posts: 1516 Germany	Re: how 2 reduce the systematic offset of a folded cascod comparator Reply #2 - Apr 8^th, 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.
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loose-electron Senior Fellow Offline Best Design Tool = Capable Designers Posts: 1638 San Diego California	Re: how 2 reduce the systematic offset of a folded cascod comparator Reply #3 - Apr 17^th, 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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