advantages folded cascode operational amplifier
The Folded Cascode Architecture allows to put a cascode differential pair in a low supply voltage environnement, thereby allowing to also cascode the output load, and so to obtain high gain stage, still in a low voltage environnement.
However, this architecture, as every cascoded architecture suffers from limited output swing compared to their non-cascoded counterparts.
The foded-cascode architecture also have the advantage of reducing the input capacitance of the circuit. In fact, while in non-cascoded differential pair structure, the cgd capacitance is multiplied by the amplifier gain when seen at the input, it is only multiplied by the casode gain in cascoded differential pair (approximately gm_diff/[gm_casc+gmb_casc] ). So, it lowers the previous stage's load, or reduce the output load in feedback, thus providing higher bandwith than the non-cascoded counterpart.