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Katsufumi NAKAMURA L. Richard CARLEY
The paper presents an enhanced fully differential folded-cascode op-amp topology that achieves improved dc gain and common-mode rejection without sacrificing slew rate. The large-signal operation of the new topology is completely symmetric, 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 gmro (typically 1-2 orders of magnitude) lower than the differential-mode output impedance, significantly improving the common-mode rejection ratio. The predicted performance is verified by simulations and preliminary experimental results.