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:
May. 10, 1994
Filed:
Aug. 11, 1993
Donald M Archer, Sunnyvale, CA (US);
National Semiconductor Corp., Santa Clara, CA (US);
Abstract
An improved current source having high output impedance, low saturation voltage, and less sensitivity to process parameters is achieved by having enhancement P-channel transistor devices used as current mirror, while depletion P-channel transistor devices are provided as the cascode devices. A 'diode connected' depletion device may be inserted between the enhancement gate and the drain of the current reference transistor to reduce saturation voltage. The 'diode connected' depletion device keeps the drains of the enhancement devices at a similar voltage even when the enhancement and depletion device threshold, i.e. V.sub.T, do not track over temperature or process. Thus, the current mirror circuit provides not only higher output impedance, lower saturation voltage, but is also less sensitive to process variation.