folded cascode compensation, psrr, novel, opamp, great technique

1. Internally compensated folded cascode

2. 2
Reference
• Design Techniques for Cascoded CMOS Op Amps with Improved PSRR
andCommon-Mode Input Range
• It is from 1984

3. 3
› Fig1 is bad for psrr, since the cap shorts d and g and becomes diode
connected
› Fig2 is preferable
› Fig3 is widely used at my company and industry against conventional
way of connecting miller C between o/p of 1st stage and i/p of 2nd stage

4. 4
• In folded cascode with the connection as shown in fig3, it might appear that the pole movement towards origin is lesser than conventional
• 1/(R*C)
• C is now higher than traditional miller cap connection due to higher gain which offsets decrease in R looking into source
• A snapshot from the reference is presented below