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is it good using Deep N-well for Analog circuit?

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020170

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Deep N-well better than standard N-well for analog Circuit degisn?
 

sunking

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some thing is better, some thing is worse.
 

vijay.kumarreddy

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Deep N-Well is of greater use when there is power switches in ur analog ckts.since the power swiches generates both the lateral and vertical currents .gaurdrings will collect the lateral currents effectively where as the Deep N-well collects the vertical currents .The depth of Deep N-well depends on the depeth of penetration of the vertical current carriers.

vijay
 

layout_designer

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It entirely depends on the circuit. Certain blocks deep nwell is must.
I ahve not used deep nwell in the regular analog circuits
 

YESH_23

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should have a look at chip size so that it wont be costly as deep n well has more spacing constraints
 

jcpu

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Also some people wrap noise sensitive circuits with Deep Nwell.
Upto ~10MHz it's said to be effective.

Practically, it's not easy to completely wrap big piece of analog circuit blocks
by deep Nwell
since some designers tend to deploy Nwell not tighted to AVDD.

Some foundry does has certain "Isolation measurement report"
in their technical information center. You might want to take a look.
The isolation should be similar even if you use very different generation
of process.
 

vonleo

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Deep N well need large silicon area
 

Mline7

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Deep Nwell provides you with a mean to isolate NMOS bulk by placing a Pwell into it.

It could be very effective for noise issues, and also to improve linearity and thus THD of your amplifier when you're using an NMOS differential apir within your amplifier.

But you should be carefull using it, because it is area consumming, so use it only when required.
 

pyrite

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Deep Nwell has better noise isolation. But you need to put the extra cost (extra mask and steps) in mind.
So it is a trade off.
 

omsi

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020170 said:
Deep N-well better than standard N-well for analog Circuit degisn?

Deep Nwell is used only when u require high threshold transistors.It is not like it is better or that is better it depends on the design requirements.If the designer says to use deepnwell then u hav to use deep N-well.
 

sambireddy

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deepNwell serves needy when the transistors inside are very sensitive to the substrate noise or if there is lot of fluctuations in the power . deep nwell penetrates deep into the substrate almost cutting of the substrate. it also depends on the placement of the transistors, suppose if the transistors are placed near to photodoide then its almost compulsory to use deep nwell to avoid the heavy flow of electrons in the substrate generated due to the photo emission.
 

zhancangF117

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deep nwells are usually used in RF chip design to protect device from substrate noise and inject noise to substrate.
but it will cost a lot , for TSMC this layer will cost about $100
 

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