Re: A simple question
Normally,the the bulk of NMOS is connected to GND.
Of course,I know some process can support the bulk of NMOS connect to it's source(not GND).
Added after 24 minutes:
The transistors must be operation at satuation region,so:
1.M1 operation in satuation region:
Vin,CM<Vdd-Vdsat1-Vsg2
2.M2 operation in satuation region:
Vp-Vin,CM-|Vth2|<Vp-Vth4
--->Vin,CM>Vth4-Vth2
To improve ICMR,connect the M2&M3 bulk to VDD.
To improve PSRR and noise,connect the M2&3 bulk to source.