Low-power voltage regulator circuit with fast transient response, and corresponding method of operation

A voltage regulator circuit, comprising:

• an input differential stage comprising:
• a biasing current generator configured to provide a biasing current for a biasing node;
• an input differential pair of transistors comprising a first input transistor and a second input transistor, both coupled to the biasing node;
• a pair of cascode transistors comprising a first cascode transistor coupled to the first input transistor at a first node, and a second cascode transistor coupled to the second input transistor at a second node;
• and
• an active load circuit coupled to the pair of cascode transistors, wherein an output node of the input differential stage is intermediate the first cascode transistor and the active load circuit;
• an output stage comprising an output transistor having a conductive channel disposed between a supply node and an output node of the voltage regulator circuit, the output transistor having a gate terminal coupled to the output node of the input differential stage, and configured to pass an output current from the supply node to the output node of the voltage regulator circuit;
• a replica transistor having a conductive channel between the supply node and a further node, the replica transistor having a gate terminal coupled to the gate terminal of the output transistor, and configured to pass a scaled-down replica current of the output current from the supply node to the further node;
• and
• a current mirror coupled to the replica transistor, and configured to sense the scaled-down replica current, sink from the first node a first additional biasing current based on the scaled-down replica current, and sink from the second node a second additional biasing current based on the scaled-down replica current.