这个sansen的书中提到,rail to rail 指输入电压范围可以是全电压范围,通过NMOS和PMOS对实现。当输入为低电压时,PMOS pair 工作,gmtotal=gmp,当输入为高时,nmos pair 工作,gmtotal=gmn,当输入为中间范围时,owing to gmtotal is proportional to bias current, hence gmtotal=gmp+gmn, therefore , we need keep gm constant for different input voltages.
这个sansen的书中提到,rail to rail 指输入电压范围可以是全电压范围,通过NMOS和PMOS对实现。当输入为低电压时,PMOS pair 工作,gmtotal=gmp,当输入为高时,nmos pair 工作,gmtotal=gmn,当输入为中间范围时,owing to gmtotal is proportional to bias current, hence gmtotal=gmp+gmn, therefore , we need keep gm constant for different input voltages.