floating n well
If nwell is floating, the current through PMOST may drive forward the P+/NWELL diode, the emmiter of the parasitic vertical pnp bipolor. Thus comes the susceptibility to latchup. Even latchup is not occur, the subthreshold characteristic of the PMOST will be deteriorated, the off-leakage of PMOST will increase.
Hi, bastos4321,
I suppose you are talking about source-connected nwell rather than floating nwell. I never seen an analog amplifier with floating nwell in bulk silicon process. To cancel the body effect of PMOS, the substrate of PMOST(nwell) is connected to its source, but not floating.