Method and circuit for controlled gain reduction of a gain stage

摘要

The present document relates to multi-stage amplifiers, such as linear regulators or linear voltage regulators (e.g. low-dropout regulators) configured to provide a constant output voltage subject to load transients. A multi-stage amplifier is described. The multi-stage amplifier comprises a first amplification stage configured to provide a stage output voltage at a stage output node. Furthermore, the amplifier comprises an intermediate amplification stage comprising an amplifier current source configured to provide an amplifier current and an amplifier transistor arranged in series with the amplifier current source. A gate of the amplifier transistor is coupled to the stage output node of the first amplification stage. The intermediate amplification stage is configured to provide an amplified or attenuated stage output voltage at a midpoint between the amplifier current source and the amplifier transistor.

主权项

1. A multi-stage amplifier comprising
a first amplification stage configured to provide a stage output voltage at a stage output node; an intermediate amplification stage comprising
an amplifier current source configured to provide an amplifier current; andan amplifier transistor arranged in series with the amplifier current source; wherein a gate of the amplifier transistor is coupled to the stage output node of the first amplification stage; wherein the intermediate amplification stage is configured, to provide an amplified or attenuated stage output voltage at a midpoint between the amplifier current source and the amplifier transistor; and a gain control circuit configured to reduce an effective output impedance of the amplifier transistor by providing a current feedback to the midpoint;wherein
the gain control circuit comprises a control transistor; a gate of the control transistor is coupled to the stage output node of the first amplification stage; an input port of the control transistor is coupled to an input port of the amplifier transistor; the gain control circuit comprises current mapping means configured to map a current at an output port of the control transistor to the midpoint; and an output port of the amplifier transistor is coupled to the midpoint.