The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 31, 2006
Filed:
Aug. 03, 2005
Shengming Huang, Gourock, GB;
Shengming Huang, Gourock, GB;
National Semiconductor Corporation, Santa Clara, CA (US);
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.