Method and apparatus for maintaining stability in a circuit under variable load conditions

A voltage regulator, comprising:

• an operational amplifier having an output terminal;
• a capacitor coupled to said output terminal of said operational amplifier to provide frequency compensation for said operational amplifier;
• a variable resistance coupled to said capacitor to maintain stability within the voltage regulator under variable load conditions, wherein said variable resistance includes a first transistor having an input terminal and first and second output terminals, said first transistor displaying a resistance between said first and second output terminals that varies in response to a signal applied to said input terminal of said first transistor, said first output terminal of said first transistor being coupled to said capacitor;
• and
• a second transistor having an input terminal and first and second output terminals, said input terminal of said second transistor being coupled to said output terminal of said operational amplifier and said first output terminal of said second transistor being coupled to said input terminal of said first transistor.

A method for maintaining stability in a circuit, comprising:

• providing a circuit having a transfer function including at least one pole and a movable zero within an active frequency range of the circuit;
• feeding back a first output signal of the circuit to control a DC level of the circuit;
• and
• feeding back a second output signal of the circuit to adjust frequency values of the pole and movable zero.