A circuit topology for
gain boosted high-swing folded
cascode has been improved to maximize the available
dynamic range in applications having low supply
voltage requirements. The circuit includes an improved
gain boost
amplifier that maximizes the available
dynamic range for applications having low supply
voltage requirements. The improved
gain boosting
amplifier includes a differential pair of input transistors connected to a
current mirror, wherein a pair of current sources
supply current to each lead of the
current mirror. One lead of the
current mirror is level-shifted by a
transistor coupled to another
current source, wherein the
coupling of the
transistor and the
current source form the output of the
amplifier. Effectively, the amplifier consists of an effective level shift and a series common-drain, common-gate amplifier. A reduction in
transconductance gm from the series combination is compensated by a current mirror ratio (K:1) between the level shift and the common-drain, common-gate amplifier. Specifically, the size of one of the transistors in the differential pair is a multiple integer (K) times the size of the other
transistor in the differential pair. In addition, the size of one of the transistors in the current mirror is a multiple integer (K) times the size of the other transistor in the current mirror. Moreover the amount of current supplied by the second
current source is a multiple integer (K) times the amount of current provided by the first current source.