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SP24
Joined: 05 Oct 2007
Posts: 26
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 28 Aug 2008 7:02 Need suggestions on this matching pattern |
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I am trying to match an N-mos diff pair(10 fingers each) in the following pattern,
A B A B A B A B A B
s d s d s d s d s d s d s d s d s d s d
B A B A B A B A B A
s d s d s d s d s d s d s d s d s d s d
Is this a correct way of matching? or should i change the arrangement of the trans?
Express your views.
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electronrancher
Joined: 24 Mar 2002
Posts: 474
Helped: 34
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| 28 Aug 2008 17:24 Need suggestions on this matching pattern |
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That layout will be fine. You could also alternate sd ds but the matching texts say that a single repeated instance offers better matching than any change in orientation.
For instance, if LDD is an angled implant, alternating the orientations will make matching worse as some devices will get deeper LDD than others. Again, if equal number of A's and B's are affected equally it should wash out - but the safest rule is to just repeat a single instance in the same orientation.
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SP24
Joined: 05 Oct 2007
Posts: 26
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| 29 Aug 2008 6:29 Re: Need suggestions on this matching pattern |
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| But if i place the transistors as (source)-A-(Drain) (Drain)-B-(source) the current will flow in the opposite direction.So i felt arranging them as Source drain source drain is better.correct me if i am wrong
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k_90
Joined: 25 Jan 2006
Posts: 114
Helped: 17
Location: Scotland,GB
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| 29 Aug 2008 13:15 Re: Need suggestions on this matching pattern |
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For a Diff pair I would cross couple the gates.
A B A B A | B A B A B
X
B A B A B | A B A B A
OR
A A A A A | B B B B B
X
B B B B B | A A A A A
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I am trying to match an N-mos diff pair(10 fingers each) in the following pattern,
A B A B A B A B A B
s d s d s d s d s d s d s d s d s d s d
B A B A B A B A B A
s d s d s d s d s d s d s d s d s d s d
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alexan56
Joined: 19 Aug 2008
Posts: 9
Helped: 2
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| 29 Aug 2008 13:51 Re: Need suggestions on this matching pattern |
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You can contact the component engineers through the website beganto.com for the solution of the problem.
I am sure you will get the solution. Do let me know if you need anything more.
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PoojanWagh
Joined: 27 Aug 2008
Posts: 20
Helped: 4
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| 29 Aug 2008 13:59 Re: Need suggestions on this matching pattern |
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| SP24 wrote: |
I am trying to match an N-mos diff pair(10 fingers each) in the following pattern,
A B A B A B A B A B
s d s d s d s d s d s d s d s d s d s d
B A B A B A B A B A
s d s d s d s d s d s d s d s d s d s d
Is this a correct way of matching? or should i change the arrangement of the trans?
Express your views. |
Your layout will work. It will cancel out linear gradients. However, if you iterate on the layout, you can cancel higher-order gradients (square or cube).
Can you make them 8 fingers instead of 10? If so, I would do:
| Code: |
A B B A
B A A B
B A A B
A B B A
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You'll want to put dummies around the edges:
| Code: |
D D D D D D
D A B B A D
D B A A B D
D B A A B D
D A B B A D
D D D D D D |
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electronrancher
Joined: 24 Mar 2002
Posts: 474
Helped: 34
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| 29 Aug 2008 15:50 Need suggestions on this matching pattern |
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Square or cube gradients? I've never heard of such a thing in all the fabs I have used. Do you have any reputable information or link? It kind of sounds like somebody's research project rather than a substantial effect you see in production IC's.
What percentage of the total variation of the oxide thickness can be accurately modelled as a second order profile such as square or cube?
Enlighten me if you would.
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rfsystem
Joined: 25 Feb 2002
Posts: 798
Helped: 85
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| 29 Aug 2008 21:46 Re: Need suggestions on this matching pattern |
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O boys, do not forget that the edge of an NWELL is far enough. Less than 10um will have a 10mV range effect.
In newer processes I have seen wafer distribution which are more uniform but the local non uniformity gets higher.
Seems that the "best gradient pattern" gets out of fashion.
Metal pattern above also make mechanical stress. Not forget about STI. The biggest mechanical stress factor.
If want to come significant below 1mV think of calibration. That is a more rich full land with some uV beauties.
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