How to connect CMOS Body( Bulk) connection of several mosfets in layout

[Ali263]

I have to to layout of 2 stage amplifer in cadence 65nm. For reference i am given a design in which i am feeling difficulty. In layout all mosfet bodytie_type is left to none.
I was wondering how can the bulk be connected to gnd or vdd if all bodytie_type is selected to be none?

Secondly, if we are having9 mosfets in a design do we have to connect bulk of every mosfet separately to gnd or vdd?

In picture you can see the main differential and dummy mosfet pair where bulk is grounded but in layout bodytie_type is none?

 

[deep_sea]

The bulk connection is not the easiest thing to do in layout. You have to connect a certain layout (depends on technology). It might be ptap or ntap very close to the pwell of each nmos transistor. You have to ask a senior or someone who uses the technology to show you an example of connecting bulk of a single transistor then you can follow the procedure in all transistors.

 

[bkdraster]

Is your AVSS the substrate's voltage ? If that's the case, create a guard ring around your diff pair including the dummies. It's quite rare where you use the mosfet's default guardrings due to area constraints. Because if you open the guard ring options, it will bring bulk connection on each individual transistor which is cause your layout area to be bigger. Therefore you don't need to connect each transistor separately. Guard ring around the whole structure is sufficient enough. If you want to better connection and less resistance you can increase number of contacts of the guard ring but it can also increase noise on substrate. It's little bit trade-off as always.