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:
Jun. 27, 1989
Filed:
Dec. 09, 1987
Richard E Hester, Eden Prairie, MN (US);
Tuan V Ngo, Eden Prairie, MN (US);
VTC Incorporated, Bloomington, MN (US);
Abstract
A bias current cancellation circuit provides current to the bases of a pair of transistors forming a differential amplifier. A transistor of matched characteristics to the differential amplifier pair is operated so that its base current replicates the base currents of the differential transistor pair. This replicated base current is inverted by a current mirror which is connected to the bases of the differential transistional pair. A second order cancellation error caused by base current differences in the current mirror is cancelled by a feedback circuit so that only the base current of the matching transistor affects the currents supplied to differential amplifier.