Apparatus and method for a high PSRR LDO regulator

Details Apparatus and method for a high PSRR LDO regulator Apparatus and method for a high PSRR LDO regulator

2006-10-31

2006-10-31

Vu, Bao Q. (Department: 2838)

Electricity: power supply or regulation systems

Self-regulating

Using a three or more terminal semiconductive device as the...

C323S314000, C323S315000

Reexamination Certificate

active

07129686

ABSTRACT:
A tail current source is provided. The tail current source may be used in amplifiers, in an error amplifier of an LDO, or the like, to achieve high PSRR. The tail current source includes a first current mirror, a capacitor, a resistive device, and a current mirror circuit. The current mirror circuit is operable to provide the tail current from an input current. The first current mirror is an n-type current mirror which diverts a small fraction of the DC current from the current mirror circuit. The capacitor and the resistive device are coupled in series with each other, and are coupled between VDD and the common gate node of the transistors in the n-type current mirror. Accordingly, the gates of the transistors in the first current mirror follow AC variations in VDD. This way, the effects of AC variations in VDD on the tail current are approximately cancelled.

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National Semiconductor Datasheet, “LP3990—150mA Linear Voltage Regulator for Digital Applications,” Sep. 2005, pp. 1-13.

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