voltage divider using pmos

[newbie_1]

hi,
when i use diode connected pmos transistors in series to divide the voltage , is it necessary to let the transistors be in saturation region? that is, is it necessary that vdd>n* vthp ? when simulation, if they are not turned on ,still they can output the right voltage.
thanks

 

[sunking]

yes, it is better to make all of them turn on.

 

[nxing]

the reason?

 

[rfsystem]

The voltage division by n works from subthreshold (VDSAT<100mV) up to full saturation. The most important fact not mention is that all PMOS have to have the same source-bulk voltage. If an psub process is used PMOS have separateNWELLs. So connect every PMOS source of the divider by n to its bulk/NWELL.