OPAMP input common mode voltage in MOS-C integrator

[neoflash]

In a couse material, I read author stated that MOS-C integrator will suffer from variable input common mode. And it is said that R-C integrator will not.

Could anyone help me explain?

thanks,
Neoflash

 

[sunking]

the most fet Rdson depond on the Vds.

 

[neoflash]

should not their dc bias be the same, since the other side impedance is infinity?

 

[walker8764]

Rdson do depend on Vds :
Ron = L/[µCoxW(Vgs-Vt-Vds)]
but how the variance of Rdson effect the change of common mode voltage?

 

[daisyinfall]

The book by P.E.Allen may help,and there is clearly explation in chapter 4.

Regards!