Frequency compensation circuit for low dropout regulators
AssigneeLinear Technology Corporation
InventorsRobert C. Dobkin, Carl T. Nelson, Dennis P. O'Neill
Life of this patent
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Abstract
A three terminal control circuit for a low dropout voltage regulator having a PNP pass transistor is provided. The control circuit is capable of pulling the base drive point down to a voltage of 3.0 volts or less to permit a current limiting resistor to be inserted between the base drive point and the base of the PNP pass transistor. The control circuit includes a pair of small-valued capacitors for providing stable operation with different output capacitors. The control circuit can also be used with p-channel FET pass transistors.
Claims7
A frequency compensation circuit for a voltage regulator circuit, the voltage regulator circuit including a drive terminal, a feedback terminal and a ground terminal, an error signal generating circuit connected to the feedback terminal and the ground terminal and having an output node at the collector of an NPN transistor, the frequency compensation circuit comprising:
- a first capacitor coupled between the output node and the base of the NPN transistor, the first capacitor providing a rolloff in the gain of the error signal generating circuit;
- and
- a second capacitor coupled between the base of the NPN transistor and the feedback terminal, the second capacitor providing a zero which cancels the pole generated by the first capacitor at a frequency which allows regulator loop gain to fall well below unity.
Dependencies are inferred from the claim text.