Adaptive dropout for a low dropout (ldo) regulator circuit

A circuit, comprising:

• a voltage regulator circuit receiving a supply voltage and an adjustable control signal to generate a DC supply voltage from the supply voltage as a function of the adjustable control signal;
• a low dropout (LDO) regulator circuit receiving the DC supply voltage and a first reference voltage to generate a regulated output voltage from the DC supply voltage as a function of the first reference voltage;
• wherein the LDO regulator circuit includes a power transistor having drain where the regulated output voltage is generated and a gate that receives a gate voltage;
• and
• a headroom control circuit comprising:
• a replica transistor in a trans-diode configuration, wherein the replica transistor is a scaled replica of the power transistor, the replica transistor having a source coupled to a drain of the power transistor;
• a resistor connected to a drain of the replica transistor and biased by a bias current to generate a gate reference voltage;
• and
• a control signal generator circuit configured to generate the adjustable control signal as a function of a difference between the gate voltage and the gate reference voltage.