Low dropout voltage regulator with improved voltage controlled current source

A LDO voltage regulator comprising:

• a differential amplifier circuit having a pair of input terminals and an output terminal, one input terminal coupled to a predetermined reference voltage;
• an intermediate amplifier circuit having an output terminal and an input terminal coupled to the output terminal of the differential amplifier circuit;
• and
• an output pass circuit including a pass transistor and an output capacitor, the pass transistor having a control terminal coupled to the output terminal of the intermediate amplifier circuit, an input terminal coupled to a power supply and an output terminal as a voltage output node, the output capacitor coupled between the voltage output node and a ground reference;
• a feedback circuit including a pair of ladder resistors coupled in series between the voltage output node and the ground reference, a node between the ladder resistors coupled to the other input terminal of the differential amplifier circuit;
• and
• a voltage controlled current source (VCCS) having an input terminal coupled to the voltage output node and an output terminal coupled to the node between the ladder resistors, wherein
• the VCCS includes four NMOS field effect transistors MN1, MN2, MN3 and MN4, a current mirror and a compensation capacitor Cc, a gate electrode of the MN1 is coupled to a first predetermined voltage Vb1 and a source electrode of the MN1 is grounded, a gate electrode of the MN2 is coupled to the first predetermined voltage Vb1 and a source electrode of the MN2 is grounded, a gate electrode of the MN3 is coupled to a second predetermined voltage Vb2, a source electrode of the MN3 is coupled to a drain electrode of the MN1 and a drain electrode of the MN3 is coupled to an input terminal of the current mirror, a gate electrode of the MN4 is coupled to the second predetermined voltage Vb2, a source electrode of the MN4 is coupled to a drain electrode of the MN2 and a drain electrode of the MN4 is coupled to an output terminal of the current mirror, the drain electrode of the MN4 serves as the output terminal of the VCCS, one terminal of the compensation capacitor Cc is coupled to the drain electrode of the MN2 and the other terminal of the compensation capacitor Cc serves as the input terminal of the VCCS.