How to remove Vbs of mosfet.

Question

While simulate Cascode Current Mirror circuit. I run .op and this Log come up with vbs different 0, although I tried to direct connect to ground but it still have value, it lead to change Vgs, Vth, ... How can I remove it to 0. Thanks all. My process is 22nm of HP.

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[edited by: anaen1310200 at 1:39 PM (GMT -4) on 7 Jul 2024]

Achim · Accepted Answer

Hello, 
 in your cascode, the sources of M1 and M2 have to be at some positive voltage (~ 1,1V in your case). If the source is at 1,1V and you connect bulk to GND, the voltage beween bulk and source (Vbs) is inevitably at -1,1V. 
 You will get Vbs = 0V if you connect bulk to source, not bulk to GND. 
 best regards 
 Achim)