An enhanced fully differential folded-cascode op amp

This paper presents an enhanced fully differential folded-cascode op-amp topology that achieves improived dc gain and common-mode rejectioun without sacrificing slew rate. The large-signal operation of a new topology is completely symmetricn providing equal positive and negative slew-rate behavior by making use of active current mirrors to bias the outputs rather than bias current sources as normally found in fully differential folded-cascode op amps. An additional advantage of the enhanced topology is that its common-mode output impedance is a factor of g m r o (typically 1-2 orders of magnitude) lower than the differential-mode output impedance, significantly improving the common-mode rejection ratio