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about mos bulk connect

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gingerjiang

gingerjiang

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hi all

when designing analog circuits using mos, the bulk should be connected to power supply
but when layout, mos' bulk should be connected to power supply locally? or all mos' bulk should be connected together, then be connected to off chip voltage through pad? so we may make the bulk potential is quiet, isn't disturbed by on chip power supply?

thanks
 

If additional pad is allowed, I would prefer all mos' bulk connected together, then connected to off chip voltage through pad.
If no additional pad, mos' bulk on sensitive blocks should not locally connected to supply. They can eventually joined at top level, as top level normally has supply filters that can help to filter out some noise, instead to moving into mos' bulk terminal.
 

    gingerjiang

    gingerjiang

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I just can't figure out what your problem is.???
 

sengyee88 said:
If additional pad is allowed, I would prefer all mos' bulk connected together, then connected to off chip voltage through pad.
If no additional pad, mos' bulk on sensitive blocks should not locally connected to supply. They can eventually joined at top level, as top level normally has supply filters that can help to filter out some noise, instead to moving into mos' bulk terminal.
Click to expand...
but if the bulk is apart from power supply, the Vbs will not zero, and the drain current will be influenced assuming bulk is quiet, while power supply is noisy
 

vijay.kumarreddy said:
Genarally for pmos the bulk is connected to the vdd and for nmos bulk id to vss ,in some cases the bulks are connected to its respective sources.
Click to expand...

i have got a help from someone who said that the pmos's bulk may be connected to vdd locally, but the nmos's bulk should be connected to a quiet power, if possible, it should be corrupted

ginger
 

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